test(keymaps): headless Neovim harness for buffer-local bindings + CI

`scripts/test-keymaps.sh` boots `nvim --headless` against a scratch
wiki, sources `scripts/test-keymaps.lua`, and asserts the post-state
of each buffer-local mapping registered by `ftplugin/vimwiki.vim` +
`lua/nuwiki/keymaps.lua`.

The harness covers the bindings that actually have observable effects
on the buffer or cursor:

- **Lists** (LSP round-trip): `<C-Space>` / `<C-@>` / `<Nul>` toggle,
  `gln` cycle, `glx` reject, plus a `[X]→[ ]` round-trip.
- **Tasks**: `gnt` jumps to the next unfinished `[ ]`.
- **Headings** (LSP round-trip): `=` adds a level, `-` removes one,
  `=` on h6 clamps without growing.
- **Header nav** (pure Lua): `]]` next, `[[` prev, `]u` parent.
- **Link nav** (pure Lua): `<Tab>` to the next `[[…]]`.
- **`<CR>` two-step**: first press wraps a bare word as `[[word]]`
  and stops (matches vimwiki's review-then-follow).
- **Bullet continuation**: `o` / `O` keep the marker, and `o` on a
  `[ ]` line carries the checkbox forward.

Each case sets buffer lines, places the cursor (1-based), fires
`nvim_feedkeys` with `replace_termcodes`, waits long enough for the
LSP `executeCommand` round-trip (800 ms by default; 100 ms for the
pure-client maps), and asserts either the resulting lines, a specific
line, the cursor's new line, or the buffer's new name.

Output goes via `$NUWIKI_KEYMAP_RESULTS` (env-var IPC keeps it
robust to `--clean -u` argument parsing). Exit code mirrors the
harness: 0 on green, 1 on any FAIL. Local run yields:

  SUMMARY: 19 passed, 0 failed

CI: new `keymaps` job in `.gitea/workflows/ci.yaml` installs Neovim
and runs the script, so a regression in `lua/nuwiki/keymaps.lua`,
`autoload/nuwiki/commands.vim`, or the LSP command surface is caught
on every push.

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

.gitea/workflows/ci.yaml

@@ -55,3 +55,26 @@ jobs:
           restore-keys: |
             ${{ runner.os }}-cargo-test-
       - run: cargo test --workspace --all-targets
+
+  keymaps:
+    name: editor keymaps
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: dtolnay/rust-toolchain@1.83
+      - uses: actions/cache@v4
+        with:
+          path: |
+            ~/.cargo/registry
+            ~/.cargo/git
+            target
+          key: ${{ runner.os }}-cargo-test-${{ hashFiles('**/Cargo.lock', '**/Cargo.toml') }}
+          restore-keys: |
+            ${{ runner.os }}-cargo-test-
+      - name: install neovim
+        run: |
+          sudo apt-get update -qq
+          sudo apt-get install -y --no-install-recommends neovim
+          nvim --version | head -1
+      - name: run keymap harness
+        run: ./scripts/test-keymaps.sh