phase 9: editor glue — plugin, LSP wiring, install, health, docs

P5 + P6 resolved (SPEC §11): Neovim 0.11+ and Vim 9.1+.

Universal Vim entry:
- plugin/nuwiki.vim dispatches Vim vs Neovim. Neovim path waits for
  the user's `require('nuwiki').setup()` call; Vim path starts the
  LSP client on `FileType vimwiki` and exposes `:NuwikiInstall`.
- ftdetect/nuwiki.vim associates `*.wiki` with the `vimwiki` filetype.
- ftplugin/nuwiki.vim sets commentstring + comments + formatoptions +
  suffixesadd + iskeyword, with a clean `b:undo_ftplugin`.
- syntax/nuwiki.vim ships default `@vimwiki*` highlight links for the
  semantic-token legend (with `level1..6` + `centered` modifiers),
  plus a minimal regex fallback so static highlighting works before
  the LSP attaches.

Lua glue (Neovim 0.11+):
- init.lua exposes setup() / install() / health() — wiring only per
  SPEC §6.2.
- config.lua holds the §7.5 schema (wiki_root / file_extension /
  syntax / log_level) and a tbl_deep_extend apply().
- lsp.lua registers via `vim.lsp.config{} + vim.lsp.enable` on 0.11+;
  falls back to a FileType autocmd calling `vim.lsp.start` on older
  builds. Root dir walks up for `.git` / `.nuwiki`, then uses
  wiki_root.
- install.lua does target-triple detection (Linux gnu/musl x x86_64/
  aarch64, macOS arm/x86, Windows), curl+tar download from the
  release URL, cp/chmod into bin/, with a cargo fallback. Honours
  `g:nuwiki_build_from_source`.
- health.lua implements `:checkhealth nuwiki` per §7.6.

VimL glue (Vim 9.1+):
- autoload/nuwiki/lsp.vim follows §7.4 preference order:
  vim-lsp (calls `lsp#register_server`) → coc.nvim (prints the
  coc-settings.json snippet) → error.
- scripts/download_bin.vim mirrors the Lua installer for Dein /
  vim-plug build hooks — same target triples, same download →
  fallback → cargo build chain.

Help: doc/nuwiki.txt with tags for install (lazy.nvim / vim-plug /
Dein), config options, health, LSP feature list, `:NuwikiInstall`.

Rust workspace unchanged this phase; 172 tests still green locally.

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

autoload/nuwiki/lsp.vim

@@ -1,2 +1,75 @@
 " autoload/nuwiki/lsp.vim — Vim (non-Neovim) LSP client wiring.
-" Implementation deferred to Phase 9 (Editor Glue).
+"
+" Spec §7.4 preference order:
+"   1. vim-lsp (matoto/vim-lsp)
+"   2. coc.nvim
+"   3. Print an error if neither is available.
+
+let s:started = 0
+
+function! nuwiki#lsp#start() abort
+  if s:started
+    return
+  endif
+  let s:started = 1
+
+  let l:bin = s:bin_path()
+  if !executable(l:bin)
+    echohl ErrorMsg
+    echom 'nuwiki: language server not found at ' . l:bin
+    echom 'Run :NuwikiInstall to install the binary'
+    echohl None
+    return
+  endif
+
+  if exists('*lsp#register_server')
+    " vim-lsp
+    call lsp#register_server({
+          \ 'name': 'nuwiki',
+          \ 'cmd': {server_info -> [l:bin]},
+          \ 'allowlist': ['vimwiki'],
+          \ 'config': { 'settings': { 'nuwiki': s:settings() } },
+          \ })
+    return
+  endif
+
+  if exists(':CocConfig') == 2 || exists('*coc#config')
+    " coc.nvim — coc reads its server list from coc-settings.json.
+    " We can't inject it dynamically without owning the file, so just point
+    " the user at the snippet.
+    echohl WarningMsg
+    echom 'nuwiki: coc.nvim detected. Add this to your coc-settings.json:'
+    echom '  "languageserver": {'
+    echom '    "nuwiki": {'
+    echom '      "command": "' . l:bin . '",'
+    echom '      "filetypes": ["vimwiki"]'
+    echom '    }'
+    echom '  }'
+    echohl None
+    return
+  endif
+
+  echohl ErrorMsg
+  echom 'nuwiki: no supported LSP client found.'
+  echom 'Install vim-lsp (https://github.com/prabirshrestha/vim-lsp)'
+  echom 'or coc.nvim (https://github.com/neoclide/coc.nvim).'
+  echohl None
+endfunction
+
+function! s:bin_path() abort
+  if exists('g:nuwiki_binary_path') && filereadable(g:nuwiki_binary_path)
+    return g:nuwiki_binary_path
+  endif
+  let l:plugin_dir = fnamemodify(resolve(expand('<sfile>:p')), ':h:h:h')
+  let l:suffix = has('win32') ? '.exe' : ''
+  return l:plugin_dir . '/bin/nuwiki-ls' . l:suffix
+endfunction
+
+function! s:settings() abort
+  return {
+        \ 'wiki_root':      get(g:, 'nuwiki_wiki_root',      '~/vimwiki'),
+        \ 'file_extension': get(g:, 'nuwiki_file_extension', '.wiki'),
+        \ 'syntax':         get(g:, 'nuwiki_syntax',         'vimwiki'),
+        \ 'log_level':      get(g:, 'nuwiki_log_level',      'warn'),
+        \ }
+endfunction