feat(config): P3 config batch — group 1 (clean config + plumbing)

Config plumbing for the whole config batch (HtmlConfig + WikiConfig fields,
RawWiki deserialization, From/defaults) plus these behaviors:

- rss_name / rss_max_items: HtmlConfig fields (wired into write_rss in the RSS
  group).
- toc_link_format: build_toc_text emits [[#anchor]] (no description) for 1,
  [[#anchor|title]] for 0.
- generated_links_caption: build_links_text emits [[page|FirstHeading]] from a
  page->heading map (ops::page_captions) when enabled.
- table_reduce_last_col: column_widths clamps the last column to width 1 when
  set; threaded through table_align_edit/table_move_column_edit + commands.
- color_dic now ships a populated default palette (red/green/blue/...).
- commentstring aligned to upstream's no-space `%%%s`.
- auto_chdir (default off): :lcd into the owning wiki root on buffer enter;
  both clients (ftplugin.lua setup_auto_chdir + Vim NuwikiAutoChdir augroup),
  with config.wiki_root_for / nuwiki#commands#wiki_root_for resolvers.

Also seeded HtmlConfig fields for later groups (valid_html_tags,
list/text_ignore_newline, emoji_enable, user_htmls, color_tag_template) and
WikiConfig (create_link, dir_link, bullet_types, cycle_bullets).

Tests: toc_link_format, generated_links_caption, table_reduce_last_col,
config defaults + JSON round-trip for every new key. Full rust suite +
both keymap harnesses green.

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

crates/nuwiki-lsp/tests/commands_coverage.rs

@@ -306,7 +306,8 @@ fn nuwiki_toc_generates_nested_contents() {
     let src = "= Top =\n== Sub ==\ntext\n";
     let doc = parse(src);
     let uri = Url::from_file_path("/wiki/Page.wiki").unwrap();
-    let edit = ops::toc_edit(src, &doc, &uri, true, "Contents", 1, 0).expect("toc edit produced");
+    let edit =
+        ops::toc_edit(src, &doc, &uri, true, "Contents", 1, 0, 0).expect("toc edit produced");
     assert!(edit.changes.is_some() || edit.document_changes.is_some());
 
     let toc = ops::build_toc_text(
@@ -317,6 +318,7 @@ fn nuwiki_toc_generates_nested_contents() {
         "Contents",
         1,
         0,
+        0,
     );
     assert!(toc.contains("= Contents ="));
     assert!(toc.contains("- [[#top|Top]]"));
@@ -327,7 +329,7 @@ fn nuwiki_toc_generates_nested_contents() {
 #[test]
 fn nuwiki_generate_links_lists_all_pages_excluding_current() {
     let pages = vec!["About".to_string(), "Home".to_string(), "Notes".to_string()];
-    let text = ops::build_links_text(&pages, "Links", 1, Some("Home"), 0);
+    let text = ops::build_links_text(&pages, "Links", 1, Some("Home"), 0, None);
     assert!(text.contains("= Links ="));
     assert!(text.contains("- [[About]]"));
     assert!(text.contains("- [[Notes]]"));
@@ -345,7 +347,8 @@ fn nuwiki_generate_links_lists_all_pages_excluding_current() {
         true,
         "Generated Links",
         1,
-        0
+        0,
+        None
     )
     .is_some());
 }