fix(parity): close the 2026-06-02 re-audit config/command findings

Implements the remaining fourth-pass findings (gap doc updated):

- list_margin: rework to upstream's buffer-side meaning. Drop the
  nuwiki-only HTML em-margin (renderer field/method + render_page_html
  param removed) and prepend max(0, list_margin) leading spaces to every
  generated bullet in build_toc_text / build_links_text /
  build_tag_links_text / diary::build_index_body; headings stay at col 0.
  From<RawWiki> derives 0 for markdown wikis when unset. Negatives can't
  resolve 'shiftwidth' server-side, so they collapse to zero indent
  (documented divergence).

- diary_months: per-wiki Vec<String> (default 12 English names), threaded
  into the diary-index month labels; missing/empty slots fall back to the
  English name.

- diary_caption_level: widen u8 -> i8 so vimwiki's -1 (min: -1) parses;
  build_index_body clamps < 0 to base tree level 0.

- VimwikiRemoveDone: regain upstream's -range. All four defs are now
  -bang -range, dispatched via remove_done(bang, range, l1, l2) in both
  clients: ! -> whole buffer, explicit range -> new list_remove_done_range
  ({range:[l1-1,l2-1]}), else current list. Server remove_done_edit gained
  an Option<(u32,u32)> range that filters whole-doc victims by start line.

markdown_header_style is deferred: the generators emit vimwiki syntax only
(caption_line never writes markdown headers), so there's no markdown header
to attach the style to. Logged as the "generated-content is vimwiki-only"
intentional divergence pending a later markdown generated-content effort.

Tests: list_margin indent, markdown list_margin-0 default, diary_months
custom + fallback, negative caption_level clamp/parse, ranged remove-done
(server + both keymap harnesses). 553 lsp/core tests pass; clippy clean.

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

development/tests/test-keymaps-vim.vim

@@ -669,6 +669,26 @@ call s:record(
       \ 'cmd.VimwikiListChangeLvl_accepts_range_and_args',
       \ 'err=' . s:lcl_err)
 
+" ===== :VimwikiRemoveDone -bang -range =====
+" Upstream is `-range`; nuwiki had `-bang` only, so `:'<,'>VimwikiRemoveDone`
+" raised E481. Now `-bang -range`: a ranged invocation must parse (no E481),
+" and the `!` whole-buffer form must still work. The removal is an LSP
+" roundtrip (no server here), so assert only the attribute parse.
+call s:set_buf(['- [X] a', '- [ ] b', '- [X] c'])
+let s:rd_err = ''
+try
+  silent 1,2VimwikiRemoveDone
+  silent VimwikiRemoveDone!
+catch /E481/
+  let s:rd_err = v:exception
+catch
+  " non-E481 (e.g. no LSP attached) is expected and fine here.
+endtry
+call s:record(
+      \ s:rd_err ==# '' ? 1 : 0,
+      \ 'cmd.VimwikiRemoveDone_accepts_range_and_bang',
+      \ 'err=' . s:rd_err)
+
 " ===== :VimwikiToggleRejectedListItem -range =====
 " Was bare (range-less): `:1,3VimwikiToggleRejectedListItem` raised E481. The
 " reject is an LSP roundtrip (no server here), so assert only the attribute