feat(lsp): wire diary/auto_toc/links_space_char/list_margin; drop client-side keys

Consume several per-wiki config keys that the server deserialized but
ignored, and remove keys whose effect is purely client-side:

- diagnostics: re-publish open-doc diagnostics on
  didChangeConfiguration so a link_severity change takes effect
  immediately; fix the single-key unwrap in apply_change so a minimal
  `{ diagnostic: {...} }` payload isn't mistaken for a namespace wrapper.
- auto_toc: rebuild an existing TOC section on save (new
  ops::toc_rebuild_edit, no-op when the page has no TOC).
- diary index: honour diary_header, diary_sort and diary_caption_level
  when rendering the diary index body.
- links_space_char: apply on rename so spaces in the link target and
  the on-disk path become the configured glyph (default " " = verbatim).
- list_margin: thread the per-wiki value into render_page_html.
- remove nested_syntaxes, maxhi and diary_start_week_day from the server
  config: nested-syntax and heading highlighting are client-side, and
  the weekly diary is ISO-week based so a custom week start has no clean
  server-side meaning.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

crates/nuwiki-lsp/tests/link_health.rs

@@ -393,6 +393,27 @@ fn toc_edit_returns_none_for_empty_doc() {
     assert!(ops::toc_edit(src, &ast, &uri, true).is_none());
 }
 
+#[test]
+fn toc_rebuild_edit_only_acts_when_toc_already_present() {
+    let uri = Url::parse("file:///tmp/page.wiki").unwrap();
+
+    // No existing TOC → rebuild-on-save must not insert one.
+    let without = "= One =\n== Two ==\n";
+    let ast = parse(without);
+    assert!(
+        ops::toc_rebuild_edit(without, &ast, &uri, true).is_none(),
+        "auto_toc should not insert a TOC where none existed"
+    );
+
+    // Existing TOC → rebuild refreshes it.
+    let with = "= Contents =\n- [[#stale|Stale]]\n\n= Real =\n";
+    let ast = parse(with);
+    let edit = ops::toc_rebuild_edit(with, &ast, &uri, true).expect("rebuild edit");
+    let te = &edit.changes.unwrap()[&uri][0];
+    assert!(te.new_text.contains("[[#real|Real]]"));
+    assert!(!te.new_text.contains("Stale"));
+}
+
 // ===== links_edit =====
 
 #[test]