Remove Rust code, delegate server to nuwiki-rs repo

Delete all Rust crates (crates/) and Cargo files. The nuwiki-ls binary
is now built in the separate nuwiki-rs repository and downloaded at
install time from the Gitea release assets, with a cargo build fallback
that clones nuwiki-rs.

Update all documentation to reflect the split repo layout.

development/SPEC.md

@@ -6,16 +6,12 @@ For day-one setup see [ONBOARDING.md](ONBOARDING.md); for user-facing help see
 
 nuwiki is a vimwiki-compatible Vim/Neovim plugin backed by a Rust language
 server. The editor layers are thin clients; all parsing, navigation, and
-editing logic lives in the Rust crates and is reached over LSP.
+editing logic lives in the [nuwiki-rs](https://code.gfran.co/gffranco/nuwiki-rs)
+repository and is reached over LSP.
 
 | Property | Value |
 |---|---|
 | License | Dual MIT / Apache-2.0 |
-| MSRV | Rust 1.83 |
-| Edition / resolver | 2021 / v2 |
-| Repo | `https://code.gfran.co/gffranco/nuwiki` |
-| VCS / CI | Gitea + Gitea Actions |
-| LSP library | `tower-lsp` (tokio, stdio transport) |
 | Min editors | Neovim 0.11+, Vim 9.1+ |
 
 ---
@@ -28,42 +24,21 @@ editing logic lives in the Rust crates and is reached over LSP.
 Editor client (VimL / Lua)  — pure wiring, no logic
         │  LSP over stdio
         ▼
-nuwiki-lsp  — protocol bridge, executeCommand, document store, config
-        │
-        ▼
-nuwiki-core — lexer → parser → AST → renderer (no editor deps)
+nuwiki-ls (nuwiki-rs)     — Rust LSP server: protocol bridge, executeCommand,
+                             document store, config, parser, renderer
 ```
 
-### Crate dependency rules
+> The Rust LSP server is in the separate [nuwiki-rs](https://code.gfran.co/gffranco/nuwiki-rs)
+> repository. This plugin repo is the Vim/Neovim client layer only.
+>
+> The architecture table below is for reference — the Rust source lives in nuwiki-rs.
 
-```
-nuwiki-ls  →  nuwiki-lsp  →  nuwiki-core
-```
-
-- `nuwiki-core` never depends on `nuwiki-lsp` / `nuwiki-ls`.
-- `nuwiki-lsp` never depends on `nuwiki-ls`.
 - The VimL and Lua layers contain no logic — every command body issues a
   `workspace/executeCommand` or a built-in LSP request.
 
 ### Repository layout
 
 ```
-crates/
-  nuwiki-core/        # parser, AST, renderer — editor-independent
-    src/
-      ast/            # block.rs inline.rs link.rs span.rs visit.rs
-      syntax/         # registry.rs + vimwiki/{lexer,parser}.rs
-      render/         # html.rs
-      date.rs         # diary period math (no chrono dependency)
-  nuwiki-lsp/         # LSP backend
-    src/
-      lib.rs          # Backend, capabilities, textDocument handlers
-      commands.rs     # executeCommand dispatcher + pure edit ops
-      config.rs       # Config / WikiConfig / HtmlConfig
-      diagnostics.rs index.rs nav.rs rename.rs semantic_tokens.rs
-      diary.rs export.rs edits.rs folding.rs wiki.rs
-  nuwiki-ls/          # thin binary: starts the stdio server
-
 plugin/nuwiki.vim     # universal entry point (detects Vim vs Neovim)
 lua/nuwiki/           # Neovim layer: init, config, lsp, keymaps, commands,
                       #   folding, install
@@ -72,12 +47,15 @@ ftdetect/ ftplugin/ syntax/   # filetype detection, buffer setup, fallback HL
 doc/nuwiki.txt        # :help
 scripts/download_bin.vim      # plugin-runtime binary download (build hooks)
 development/          # dev-only tooling + this document (not shipped)
-.gitea/workflows/     # ci.yaml, release.yaml
 ```
 
 ---
 
-## 2. nuwiki-core
+## 2. nuwiki-core (nuwiki-rs)
+
+> This section documents the Rust server's internals — the source lives in
+> the [nuwiki-rs](https://code.gfran.co/gffranco/nuwiki-rs) repository. Kept
+> here as a technical reference for the LSP protocol contract.
 
 ### AST
 
@@ -199,9 +177,8 @@ raw and external URLs are never diagnosed.
 Pre-built binaries are published as Gitea release assets
 (`nuwiki-ls-{version}-{target}.tar.gz`) and fetched at install time by
 `lua/nuwiki/install.lua` (Neovim) or `scripts/download_bin.vim` (Vim build
-hooks), installed to `{plugin_dir}/bin/nuwiki-ls`. Falls back to
-`cargo build --release` when download fails or
-`g:nuwiki_build_from_source = 1`.
+hooks), installed to `{plugin_dir}/bin/nuwiki-ls`. The binary is downloaded
+from the [nuwiki-rs](https://code.gfran.co/gffranco/nuwiki-rs) releases.
 
 `plugin/nuwiki.vim` dispatches: Neovim → `require('nuwiki').setup()`; Vim →
 `nuwiki#lsp#start()` (prefers `vim-lsp`, falls back to `coc.nvim`). On Neovim
@@ -323,16 +300,12 @@ provides a no-LSP fallback):
 
 | Job | Command |
 |---|---|
-| fmt | `cargo fmt --all -- --check` |
-| clippy | `cargo clippy --workspace --all-targets -- -D warnings` |
-| test | `cargo test --workspace --all-targets` |
 | keymaps | `development/tests/test-keymaps.sh` (Neovim 0.11) + `test-keymaps-vim.sh` (Vim) |
+| calendar | `development/tests/test-calendar.sh` (Neovim) + `test-calendar-vim.sh` (Vim) |
 
-`.gitea/workflows/release.yaml` triggers on `v*` tags: cross-compiles the four
-Linux targets (gnu/musl × x86_64/aarch64) via `cross`, packages `.tar.gz`, and
-creates a Gitea release using `RELEASE_TOKEN`. macOS and Windows binaries are
-built manually and attached to the same release. crates.io publishing is not
-wired up.
+`.gitea/workflows/release.yaml` (in [nuwiki-rs](https://code.gfran.co/gffranco/nuwiki-rs))
+triggers on `v*` tags: cross-compiles the four Linux targets (gnu/musl × x86_64/aarch64)
+via `cross`, packages `.tar.gz`, and creates a Gitea release using `RELEASE_TOKEN`.
 
 A change is semver-breaking if it alters `nuwiki-core` AST nodes, the
 `SyntaxPlugin`/`Renderer` traits, the user-config schema, or removes an LSP