parity(1): vimwiki per-wiki config keys, table colspan/rowspan,

named link commands, mouse maps

Parity audit Cluster 1 — small wins.

WikiConfig (server) extended with 14 vimwiki globals:
- `index` (`g:vimwiki_index`), wired into `:VimwikiIndex` so users
  with a custom index page stem (e.g. `home`) get the right file.
- `diary_frequency`, `diary_start_week_day`, `diary_caption_level`,
  `diary_sort`, `diary_header` — diary keys (weekly/monthly/yearly
  semantics land in Cluster 4; the keys parse now so config
  migration doesn't need to wait).
- `maxhi`, `listsyms`, `listsyms_propagate`, `list_margin`,
  `links_space_char`, `nested_syntaxes`, `auto_toc` — list +
  highlight knobs the renderer/handlers can consult.

All keys threaded through `RawWiki` → `WikiConfig::from(RawWiki)`,
defaults centralised in `wiki_defaults()` so `empty()`, `from_root()`,
the legacy single-wiki path, and the `RawWiki` impl stay in sync.

Lua front-door (`lua/nuwiki/config.lua`) now documents the multi-wiki
`wikis = {…}` shape with every accepted per-wiki key — users who
prefer Lua tables no longer have to round-trip through
`init_options` raw JSON.

HTML renderer (`crates/nuwiki-core/src/render/html.rs`):
- New `table_spans()` pre-pass resolves vimwiki's `>` (col_span) and
  `\\/` (row_span) continuation markers into proper HTML
  `colspan="N"` / `rowspan="N"` attributes on the lead cell. Continuation
  cells emit nothing, matching what browsers expect.
- The old behaviour (emitting `class="col-span"` / `class="row-span"`
  as visual markers) is gone — replaced with real merging so the
  rendered HTML matches the source semantics.

Named ex-commands:
- `:VimwikiNextLink` / `:VimwikiPrevLink` — were keymapped only
  (`<Tab>`/`<S-Tab>`); now have explicit `:` commands in both editor
  paths, dispatching to new `nuwiki.commands.link_next` / `link_prev`
  pure-Vim/Lua helpers.
- `:VimwikiBaddLink` — adds the link target's file to the buffer
  list without switching focus. Goes through
  `textDocument/definition` and runs `:badd <fname>` on the resolved
  URI.

Mouse maps (opt-in via `mappings.mouse = true` in Lua or
`g:nuwiki_mouse_mappings = 1` in Vim):
- `<2-LeftMouse>` follows, `<S-2-LeftMouse>` / `<C-2-LeftMouse>`
  follow in split/vsplit, `<MiddleMouse>` adds to buflist,
  `<RightMouse>` goes back. Mirrors upstream vimwiki's defaults.

Tests: 7 new in `parity_cluster_1.rs` covering the per-wiki config
defaults + raw JSON parse, the legacy-single-wiki path, colspan
folding into a lead cell with no leftover class markers, rowspan
across rows, no-attrs when the table has no spans, and a sanity
paragraph render. Total 421 Rust tests pass; clippy clean; both
keymap harnesses still green (20 nvim + 12 vim).

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

ftplugin/vimwiki.vim

@@ -41,6 +41,9 @@ if !has('nvim')
   command! -buffer        VimwikiFollowLink             LspDefinition
   command! -buffer        VimwikiBacklinks              LspReferences
   command! -buffer        VWB                           LspReferences
+  command! -buffer        VimwikiNextLink               call nuwiki#commands#link_next()
+  command! -buffer        VimwikiPrevLink               call nuwiki#commands#link_prev()
+  command! -buffer        VimwikiBaddLink               call nuwiki#commands#badd_link()
   command! -buffer -nargs=1 VimwikiSearch  lvimgrep /<args>/ **
   command! -buffer -nargs=1 VWS            lvimgrep /<args>/ **
   command! -buffer -nargs=1 VimwikiGoto   call nuwiki#commands#wiki_goto_page(<q-args>)
@@ -181,6 +184,15 @@ if !has('nvim')
     nnoremap <silent><buffer> <Leader>whh  :call nuwiki#commands#export_browse()<CR>
     nnoremap <silent><buffer> <Leader>wha  :call nuwiki#commands#export_all()<CR>
 
+    " Mouse (opt-in via g:nuwiki_mouse_mappings = 1).
+    if get(g:, 'nuwiki_mouse_mappings', 0)
+      nnoremap <silent><buffer> <2-LeftMouse>     :call nuwiki#commands#follow_link_or_create()<CR>
+      nnoremap <silent><buffer> <S-2-LeftMouse>   :split<CR>:call nuwiki#commands#follow_link_or_create()<CR>
+      nnoremap <silent><buffer> <C-2-LeftMouse>   :vsplit<CR>:call nuwiki#commands#follow_link_or_create()<CR>
+      nnoremap <silent><buffer> <MiddleMouse>     :call nuwiki#commands#badd_link()<CR>
+      nnoremap <silent><buffer> <RightMouse>      <C-o>
+    endif
+
     " Tables
     nnoremap <silent><buffer> gqq        :call nuwiki#commands#table_align()<CR>
     nnoremap <silent><buffer> gq1        :call nuwiki#commands#table_align()<CR>
@@ -216,6 +228,9 @@ 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        VimwikiNextLink    lua require('nuwiki.commands').link_next()
+command! -buffer        VimwikiPrevLink    lua require('nuwiki.commands').link_prev()
+command! -buffer        VimwikiBaddLink    lua require('nuwiki.commands').badd_link()
 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()