phase 19: editor glue v2

Server-side:
- New `folding.rs` module with `folding_ranges(ast, total_lines)`.
  Emits one fold per top-level heading (start → line before the
  next same-or-higher-level heading, or EOF) plus one per top-level
  list block. Nested headings fold inside their parent thanks to the
  level-aware end-line computation; sublists fold implicitly via
  their parent item's source span. `FoldingRangeKind::Region` is set
  on every fold so collapsing UIs render them as section folds.
- `Backend::folding_range` handler wires the module into
  `textDocument/foldingRange`; `ServerCapabilities.folding_range_provider`
  advertises it.
- `folding::line_count` exposed for the handler and tests; treats a
  trailing newline as a virtual empty line (the line LSP positions
  use for EOF).

Editor glue (Neovim primary, Vim minimal):
- `lua/nuwiki/commands.lua` — async `workspace/executeCommand`
  wrappers for every server command shipped through Phase 18. The
  open-* family handles `{ uri }` responses by opening the file
  (with `tab` / `split` variants). `check_links` and `find_orphans`
  hand results to `setqflist` + `:copen` for quickfix-style review.
  §13.1-deferred commands (`list.changeSymbol`, table rewriters,
  `link.pasteWikilink/pasteUrl`, `colorize`) stub out with
  `vim.notify` so users get a clear "not yet implemented" signal
  instead of an LSP "unknown command" error.
- `lua/nuwiki/keymaps.lua` — buffer-local default mappings. Subgroups
  (`list_editing`, `header_nav`, `diary`, `html_export`,
  `text_objects`) flip independently via the new
  `mappings.<group>` config. Heading promote/demote uses `g=`/`g-`
  to avoid clobbering Vim's built-in `=`/`-` operators.
- `lua/nuwiki/textobjects.lua` — `ah`/`ih` (around/inside heading)
  using a buffer scan for the heading-block boundary. The four
  remaining text objects from SPEC §12.10 wait until §13.1 lands
  the table/list rewriters they share infrastructure with.
- `lua/nuwiki/folding.lua` — pure regex `foldexpr` + `foldtext`
  fallback for clients without `foldingRange`. Same heading-block
  model as the server.
- `lua/nuwiki/ftplugin.lua` — single per-buffer attach entry point.
  `folding = 'lsp'` (default) uses Neovim 0.11+'s `vim.lsp.foldexpr`,
  falling back to the regex on older versions; `'expr'` forces the
  fallback; `'off'` skips folding setup.
- `lua/nuwiki/config.lua` — extends defaults with `mappings = {...}`
  (P10 keymap layer) and `folding` (P14 resolved).
- `ftplugin/nuwiki.vim` — declares every `:Vimwiki*` / `:Nuwiki*`
  command from SPEC §12.10 by inlining `lua require(...).fn()`
  bodies (no script-local function indirection so commands stay
  callable after re-source). Plain-Vim users get only the buffer
  options; they're expected to drive the LSP via vim-lsp / coc's
  built-in commands.

Health check (§12.10 additions):
- `:checkhealth nuwiki` now reports the count of `executeCommand`
  entries the server advertises, whether `foldingRange` capability
  was negotiated, and whether the configured HTML output directory
  exists + is writable. Default keymap subgroup status is also
  surfaced.

Tests: 8 new in `phase19_folding.rs` covering empty docs, single
heading → EOF, sibling headings each getting their own fold,
nested heading bounded by parent, top-level list folds, single-line
heading non-fold, fold-kind classification, and `line_count`
semantics. Total 377 tests pass; fmt + clippy clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ftplugin/nuwiki.vim

@@ -1,8 +1,12 @@
-" ftplugin/nuwiki.vim — per-buffer settings for `.wiki` buffers.
+" ftplugin/nuwiki.vim — per-buffer settings + Phase 19 command/keymap glue.
 "
-" Keeps this minimal: only the options that affect editing ergonomics for
-" markup files. Anything richer (folding, navigation keymaps, …) ships
-" downstream once users opt in.
+" Wires up:
+"   - basic edit-time options (commentstring, suffixesadd, …)
+"   - every `:Vimwiki*` / `:Nuwiki*` command from SPEC §12.10 that has a
+"     server-side counterpart (deferred §13.1 commands stub out with a
+"     "not yet implemented" notification)
+"   - on Neovim: keymaps + text objects + folding via
+"     `nuwiki.ftplugin.attach()`
 
 if exists('b:did_ftplugin')
   finish
@@ -16,3 +20,104 @@ setlocal suffixesadd=.wiki
 setlocal iskeyword+=-
 
 let b:undo_ftplugin = 'setlocal commentstring< comments< formatoptions< suffixesadd< iskeyword<'
+
+if !has('nvim')
+  " Plain Vim — the buffer-local options above are all we ship. Vim users
+  " interact via the LSP client (vim-lsp / coc) which already exposes
+  " `:LspDefinition`, `:LspReferences`, `:LspRename`, etc.
+  finish
+endif
+
+" ===== Neovim path =====
+
+" :Vimwiki* compat — every command dispatches to a Lua wrapper in
+" `nuwiki.commands` that either issues a `workspace/executeCommand`
+" or, for client-side operations, calls `vim.lsp.buf.*` directly.
+
+command! -buffer -count VimwikiIndex      lua require('nuwiki.commands').wiki_index(vim.v.count)
+command! -buffer -count VimwikiTabIndex   lua require('nuwiki.commands').wiki_tab_index(vim.v.count)
+command! -buffer        VimwikiUISelect   lua require('nuwiki.commands').wiki_ui_select()
+command! -buffer        VimwikiDiaryIndex lua require('nuwiki.commands').diary_index()
+command! -buffer        VimwikiMakeDiaryNote          lua require('nuwiki.commands').diary_today()
+command! -buffer        VimwikiMakeYesterdayDiaryNote lua require('nuwiki.commands').diary_yesterday()
+command! -buffer        VimwikiMakeTomorrowDiaryNote  lua require('nuwiki.commands').diary_tomorrow()
+command! -buffer        VimwikiDiaryNextDay   lua require('nuwiki.commands').diary_next()
+command! -buffer        VimwikiDiaryPrevDay   lua require('nuwiki.commands').diary_prev()
+command! -buffer        VimwikiDiaryGenerateLinks lua require('nuwiki.commands').diary_generate_index()
+
+command! -buffer        VimwikiFollowLink  lua vim.lsp.buf.definition()
+command! -buffer        VimwikiGoBackLink  normal!
+command! -buffer        VimwikiSplitLink   split | lua vim.lsp.buf.definition()
+command! -buffer        VimwikiVSplitLink  vsplit | lua vim.lsp.buf.definition()
+command! -buffer        VimwikiTabnewLink  tabnew | lua vim.lsp.buf.definition()
+command! -buffer        VimwikiTabDropLink tabnew | lua vim.lsp.buf.definition()
+command! -buffer -nargs=1 VimwikiGoto       lua require('nuwiki.commands').wiki_goto_page(<q-args>)
+command! -buffer        VimwikiBacklinks   lua vim.lsp.buf.references()
+command! -buffer        VWB                lua vim.lsp.buf.references()
+command! -buffer -nargs=1 VimwikiSearch     lvimgrep /<args>/ **
+command! -buffer -nargs=1 VWS               lvimgrep /<args>/ **
+
+command! -buffer        VimwikiDeleteFile lua require('nuwiki.commands').delete_file()
+command! -buffer        VimwikiRenameFile lua require('nuwiki.commands').rename_file()
+
+command! -buffer        VimwikiNextTask              lua require('nuwiki.commands').next_task()
+command! -buffer        VimwikiToggleListItem        lua require('nuwiki.commands').toggle_list_item()
+command! -buffer        VimwikiToggleRejectedListItem lua require('nuwiki.commands').reject_list_item()
+command! -buffer        VimwikiRemoveDone            lua require('nuwiki.commands').list_remove_done()
+command! -buffer -nargs=? VimwikiListChangeLvl        lua require('nuwiki.commands').list_change_lvl()
+
+command! -buffer        Vimwiki2HTML       lua require('nuwiki.commands').export_current()
+command! -buffer        Vimwiki2HTMLBrowse lua require('nuwiki.commands').export_browse()
+command! -buffer -bang  VimwikiAll2HTML    execute (<bang>0 ? "lua require('nuwiki.commands').export_all_force()" : "lua require('nuwiki.commands').export_all()")
+command! -buffer        VimwikiRss         lua require('nuwiki.commands').export_rss()
+
+command! -buffer        VimwikiTOC               lua require('nuwiki.commands').toc_generate()
+command! -buffer        VimwikiGenerateLinks     lua require('nuwiki.commands').links_generate()
+command! -buffer        VimwikiCheckLinks        lua require('nuwiki.commands').check_links()
+command! -buffer        VimwikiFindOrphans       lua require('nuwiki.commands').find_orphans()
+
+command! -buffer        VimwikiRebuildTags       lua require('nuwiki.commands').tags_rebuild()
+command! -buffer -nargs=? VimwikiSearchTags        lua require('nuwiki.commands').tags_search(<q-args>)
+command! -buffer -nargs=? VimwikiGenerateTagLinks  lua require('nuwiki.commands').tags_generate_links(<q-args>)
+
+" §13.1 deferred — stubs notify the user instead of erroring.
+command! -buffer -nargs=1 VimwikiTable             lua require('nuwiki.commands').table_insert()
+command! -buffer        VimwikiTableMoveColumnLeft  lua require('nuwiki.commands').table_move_column_left()
+command! -buffer        VimwikiTableMoveColumnRight lua require('nuwiki.commands').table_move_column_right()
+command! -buffer -nargs=1 VimwikiColorize          lua require('nuwiki.commands').colorize()
+command! -buffer        VimwikiPasteLink           lua require('nuwiki.commands').paste_link()
+command! -buffer        VimwikiPasteUrl            lua require('nuwiki.commands').paste_url()
+
+" Canonical :Nuwiki* aliases — P10.
+command! -buffer -count NuwikiIndex      lua require('nuwiki.commands').wiki_index(vim.v.count)
+command! -buffer        NuwikiTabIndex   lua require('nuwiki.commands').wiki_tab_index(vim.v.count)
+command! -buffer        NuwikiUISelect   lua require('nuwiki.commands').wiki_ui_select()
+command! -buffer        NuwikiDiaryIndex lua require('nuwiki.commands').diary_index()
+command! -buffer        NuwikiDiaryToday     lua require('nuwiki.commands').diary_today()
+command! -buffer        NuwikiDiaryYesterday lua require('nuwiki.commands').diary_yesterday()
+command! -buffer        NuwikiDiaryTomorrow  lua require('nuwiki.commands').diary_tomorrow()
+command! -buffer        NuwikiDiaryNext      lua require('nuwiki.commands').diary_next()
+command! -buffer        NuwikiDiaryPrev      lua require('nuwiki.commands').diary_prev()
+command! -buffer        NuwikiDiaryGenerateLinks lua require('nuwiki.commands').diary_generate_index()
+command! -buffer        NuwikiFollowLink lua vim.lsp.buf.definition()
+command! -buffer        NuwikiBacklinks  lua vim.lsp.buf.references()
+command! -buffer        NuwikiDeleteFile lua require('nuwiki.commands').delete_file()
+command! -buffer        NuwikiRenameFile lua require('nuwiki.commands').rename_file()
+command! -buffer        NuwikiNextTask           lua require('nuwiki.commands').next_task()
+command! -buffer        NuwikiToggleListItem     lua require('nuwiki.commands').toggle_list_item()
+command! -buffer        NuwikiToggleRejected     lua require('nuwiki.commands').reject_list_item()
+command! -buffer        NuwikiExport             lua require('nuwiki.commands').export_current()
+command! -buffer        NuwikiExportBrowse       lua require('nuwiki.commands').export_browse()
+command! -buffer -bang  NuwikiExportAll          execute (<bang>0 ? "lua require('nuwiki.commands').export_all_force()" : "lua require('nuwiki.commands').export_all()")
+command! -buffer        NuwikiRss                lua require('nuwiki.commands').export_rss()
+command! -buffer        NuwikiTOC                lua require('nuwiki.commands').toc_generate()
+command! -buffer        NuwikiGenerateLinks      lua require('nuwiki.commands').links_generate()
+command! -buffer        NuwikiCheckLinks         lua require('nuwiki.commands').check_links()
+command! -buffer        NuwikiFindOrphans        lua require('nuwiki.commands').find_orphans()
+command! -buffer        NuwikiRebuildTags        lua require('nuwiki.commands').tags_rebuild()
+command! -buffer -nargs=? NuwikiSearchTags         lua require('nuwiki.commands').tags_search(<q-args>)
+command! -buffer -nargs=? NuwikiGenerateTagLinks   lua require('nuwiki.commands').tags_generate_links(<q-args>)
+command! -buffer -nargs=1 NuwikiGoto               lua require('nuwiki.commands').wiki_goto_page(<q-args>)
+
+" Phase 19 buffer attach: keymaps + text objects + folding.
+lua require('nuwiki.ftplugin').attach(0)