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>

SPEC.md

@@ -1,7 +1,7 @@
 # nuwiki — Project Specification
 
 > Last updated: 2026-05-10
-> Status: Phase 8 (Navigation) complete — moving to Phase 9 (Editor Glue)
+> Status: Phase 9 (Editor Glue) complete — moving to Phase 10 (CI/CD release pipeline)
 
 ---
 
@@ -588,8 +588,8 @@ These decisions are required before or during the phase indicated.
 | ~~P2~~ | ~~**MSRV**~~ | ~~Phase 0~~ | ✅ **stable-2 (Rust 1.83)** | |
 | ~~P3~~ | ~~**String representation in AST**~~ | ~~Phase 1~~ | ✅ **`String` (owned)** | |
 | ~~P4~~ | ~~**Visitor pattern**~~ | ~~Phase 1~~ | ✅ **Defined in Phase 1** | Open-recursion `Visitor` trait + `walk_*` helpers |
-| P5 | **Minimum Neovim version** | Phase 9 | 0.8 (`vim.lsp.start`) · 0.11 (`vim.lsp.config`) | 0.8 = broader compat; 0.11 = cleaner Lua API |
-| P6 | **Minimum Vim version** | Phase 9 | Vim 8.2 · Vim 9.0 · Vim 9.1 | LSP client plugins work best on 9.0+; recommend documenting 9.1 as minimum |
+| ~~P5~~ | ~~**Minimum Neovim version**~~ | ~~Phase 9~~ | ✅ **Neovim 0.11+** | Server registered via `vim.lsp.config{}` + `vim.lsp.enable`; a `vim.lsp.start` autocmd fallback is wired up but only fires when the declarative API is unavailable. |
+| ~~P6~~ | ~~**Minimum Vim version**~~ | ~~Phase 9~~ | ✅ **Vim 9.1+** | autoload glue assumes 9.1 idioms; uses `vim-lsp` first, then falls back to `coc.nvim`. |
 | ~~P7~~ | ~~**Semantic token type mapping**~~ | ~~Phase 7~~ | ✅ **Custom vimwiki-specific token types** | ~20 types (`vimwikiHeading`, `vimwikiBold`, …) + `level1`..`level6` + `centered` modifiers. Phase 9 ships default highlight groups in `syntax/nuwiki.vim` and the Lua glue. |
 | ~~P8~~ | ~~**Workspace indexing strategy**~~ | ~~Phase 8~~ | ✅ **Lazy + background with progress** | Initial scan runs as a background tokio task; nav features answer with partial data until complete; progress reported via `window/workDoneProgress`. |
 | P9 | **macOS runner** | Phase 10 | Stay manual · Register macOS runner