feat(config): on-save autoregen family — links/tags/diary-index (P2)

Added per-wiki auto_generate_links, auto_generate_tags, auto_diary_index
(default false, like upstream), wired into the did_save hook mirroring
auto_toc:

- auto_generate_links / auto_generate_tags rebuild the Generated Links /
  Generated Tags section ONLY when it already exists (new
  links_rebuild_edit / tag_links_rebuild_edit, like toc_rebuild_edit) — never
  inserts one into a page that lacks it.
- auto_diary_index regenerates the diary index page when a dated diary entry
  (not the index itself) is saved, via diary_generate_index_edit (handles the
  index file open / on-disk / absent).

auto_tags is recorded as an intentional divergence: nuwiki re-indexes tags on
every change, so the tag metadata is always fresh (no on-disk file to update).

Tests: links_rebuild_edit_only_acts_when_section_present,
tag_links_rebuild_edit_only_acts_when_index_present, config round-trip +
defaults. README/doc/lua comment updated. fmt/clippy clean; 0 Rust failures.

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

crates/nuwiki-lsp/src/lib.rs

@@ -635,6 +635,84 @@ impl LanguageServer for Backend {
             }
         }
 
+        let utf8 = self.use_utf8.load(Ordering::Relaxed);
+
+        // `auto_generate_links`: rebuild an existing `Generated Links` section.
+        if wiki.config.auto_generate_links {
+            let edit = self.documents.get(&uri).and_then(|doc| {
+                let current = index::page_name_from_uri(&uri, Some(&wiki.config.root));
+                let pages = wiki
+                    .index
+                    .read()
+                    .ok()
+                    .map(|i| i.page_names())
+                    .unwrap_or_default();
+                commands::ops::links_rebuild_edit(
+                    &doc.text,
+                    &doc.ast,
+                    &uri,
+                    &current,
+                    &pages,
+                    utf8,
+                    &wiki.config.links_header,
+                    wiki.config.links_header_level,
+                )
+            });
+            if let Some(edit) = edit {
+                let _ = self.client.apply_edit(edit).await;
+            }
+        }
+
+        // `auto_generate_tags`: rebuild an existing `Generated Tags` index.
+        if wiki.config.auto_generate_tags {
+            let edit = self.documents.get(&uri).and_then(|doc| {
+                let snap = wiki
+                    .index
+                    .read()
+                    .ok()
+                    .map(|i| commands::ops::tag_pages_snapshot(&i))
+                    .unwrap_or_default();
+                commands::ops::tag_links_rebuild_edit(
+                    &doc.text,
+                    &doc.ast,
+                    &uri,
+                    &snap,
+                    utf8,
+                    &wiki.config.tags_header,
+                    wiki.config.tags_header_level,
+                )
+            });
+            if let Some(edit) = edit {
+                let _ = self.client.apply_edit(edit).await;
+            }
+        }
+
+        // `auto_diary_index`: when a diary *entry* (a dated page, not the
+        // index itself) is saved, regenerate the diary index page.
+        if wiki.config.auto_diary_index {
+            if let Some(index_uri) = crate::diary::index_uri(&wiki.config) {
+                let is_diary_entry = uri != index_uri
+                    && wiki
+                        .index
+                        .read()
+                        .ok()
+                        .and_then(|i| i.page(&uri).and_then(|p| p.diary_period))
+                        .is_some();
+                if is_diary_entry {
+                    let body = wiki
+                        .index
+                        .read()
+                        .ok()
+                        .map(|i| crate::diary::render_index_body(&wiki.config, &i));
+                    if let Some(body) = body {
+                        let edit =
+                            commands::ops::diary_generate_index_edit(self, &index_uri, &body, utf8);
+                        let _ = self.client.apply_edit(edit).await;
+                    }
+                }
+            }
+        }
+
         // When `auto_export` is set on the resolved wiki, run
         // the equivalent of `nuwiki.export.currentToHtml` after the file
         // hits disk. Best-effort — failures are logged but do not bubble