feat(diary): -count wiki selector for diary-note + index commands (P3)

Closes the last command-cluster gap. Upstream's diary-note family
(:Vimwiki{Make,TabMake,MakeYesterday,MakeTomorrow}DiaryNote + VimwikiDiaryIndex,
and the Nuwiki* forms) carry -count=0 where the count selects the wiki number;
nuwiki's were bare. Implemented as a real end-to-end selector, reusing existing
infrastructure:

- Server (commands.rs): OptUriArg gained an optional `wiki` selector;
  resolve_diary_wiki(backend, uri, wiki) now prefers it (via the existing
  resolve_wiki_selector, which already handles a 0-indexed wiki number) over
  the buffer URI. Used by diary_open_relative + diary_open_index.

- Clients: s:diary_open / _diary_open (both) and diary_today/today_tab/
  yesterday/tomorrow/index take a count and send {wiki: count-1} when >0. All
  22 diary-note + DiaryIndex command defs across the 4 contexts are now
  -count=0 passing <count>. diary_next/prev ignore the count.

Tests: cmd.VimwikiMakeDiaryNote_has_count (test-keymaps.lua) +
cmd.Vimwiki{MakeDiaryNote,DiaryIndex}_accepts_count (test-keymaps-vim.vim).
Workspace test/clippy/fmt clean with CI flags; lua 284, vim 272/18/21.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

development/tests/test-keymaps.lua

@@ -906,6 +906,15 @@ vim.defer_fn(function()
       error(':NuwikiGenerateTags not defined')
     end
   end)
+  -- Diary-note family carries -count=0 (vimwiki's wiki selector), so
+  -- `:2VimwikiMakeDiaryNote` selects wiki #2 instead of raising E481.
+  tobj_case('cmd.VimwikiMakeDiaryNote_has_count', function()
+    local c = vim.api.nvim_buf_get_commands(0, {}).VimwikiMakeDiaryNote
+    if not c then error(':VimwikiMakeDiaryNote not defined') end
+    if c.count == nil or c.count == false then
+      error('VimwikiMakeDiaryNote missing -count: ' .. vim.inspect(c))
+    end
+  end)
   -- `:VimwikiNormalizeLink 1` (the arg is upstream's visual flag; the command
   -- is -nargs=? not -range, so no `'<,'>`) wraps the last visual selection.
   tobj_case('cmd.normalize_link_visual_wraps_selection', function()

development/vimwiki-gap.md

@@ -300,16 +300,23 @@ fix site.
   The server edits are version-less single-line, so each line's edit applies
   independently — no server protocol change needed. Covered by
   `cmd.toggle_list_item_range` in `test-keymaps.lua`.
-- [ ] **Diary-note family lacks `-count`** _(new, 2026-05-31 re-audit)_ — upstream's
-  `:Vimwiki{Make,TabMake,MakeYesterday,MakeTomorrow}DiaryNote` carry `-count=0`
-  (the count selects the wiki number); nuwiki's diary-note commands declare no
-  count in either branch. _Fix:_ `ftplugin/vimwiki.vim` diary block (both
-  branches) + thread the count into `diary_today/yesterday/tomorrow` + server
-  diary commands (accept an optional `wiki` selector). _(The `Index`/`TabIndex`
-  half is done: all four defs now use upstream's `-count=0` instead of bare
-  `-count`; `wiki_index`/`wiki_tab_index` already map the count to the wiki
-  number.)_ _(Re-audit 2026-05-31: `VimwikiDiaryIndex` is an additional instance
-  — bare in all four contexts vs upstream `-count=0` — fold it into this fix.)_
+- [x] **Diary-note family lacks `-count`** _(new, 2026-05-31 re-audit; fixed
+  same day)_ — upstream's `:Vimwiki{Make,TabMake,MakeYesterday,MakeTomorrow}DiaryNote`
+  + `VimwikiDiaryIndex` (and the `Nuwiki*` forms) carry `-count=0`, where the
+  count selects the wiki number. _Fix:_ a real wiki selector end-to-end —
+  - Server (`commands.rs`): `OptUriArg` gained an optional `wiki` selector and
+    `resolve_diary_wiki(backend, uri, wiki)` now prefers it (via the existing
+    `resolve_wiki_selector`, reused — accepts a 0-indexed number) over the
+    buffer URI; used by `diary_open_relative` + `diary_open_index`.
+  - Clients: `s:diary_open`/`diary_open` (both clients) and
+    `diary_today/today_tab/yesterday/tomorrow/index` take a count and send
+    `{wiki: count-1}` when > 0. All 22 diary-note + DiaryIndex command defs
+    across the 4 contexts are now `-count=0` passing `<count>`. `diary_next`/
+    `diary_prev` correctly ignore the count.
+  Tests: `cmd.VimwikiMakeDiaryNote_has_count` (`test-keymaps.lua`),
+  `cmd.Vimwiki{MakeDiaryNote,DiaryIndex}_accepts_count` (`test-keymaps-vim.vim`).
+  _(The `Index`/`TabIndex` family was already `-count=0`, mapping the count to
+  the wiki number via `wiki_index`/`wiki_tab_index`.)_
 - [x] **`-complete=` specs** _(new; done 2026-05-31 command-attribute pass)_ —
   upstream attaches command-line completion to several commands; nuwiki had
   none, so `<Tab>` at the `:` line never completed page / tag / colour names.