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>

crates/nuwiki-lsp/src/export.rs

@@ -203,7 +203,6 @@ pub fn render_page_html(
     today: DiaryDate,
     cfg: &HtmlConfig,
     wiki_extension: Option<&str>,
-    list_margin: i32,
     extra_vars: HashMap<String, String>,
 ) -> std::io::Result<String> {
     let date_str = match doc.metadata.date.as_deref() {
@@ -228,7 +227,7 @@ pub fn render_page_html(
         vars.insert(k, v);
     }
 
-    let mut r = HtmlRenderer::new().with_list_margin(list_margin);
+    let mut r = HtmlRenderer::new();
     if let Some(ext) = wiki_extension.filter(|e| !e.trim_start_matches('.').is_empty()) {
         // Strip the wiki extension from page links before the default resolver
         // turns them into `.html` URLs, so `[[todo.wiki]]` → `todo.html` rather