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/tests/index_and_config.rs

@@ -275,6 +275,9 @@ fn defaults_carry_vimwiki_per_wiki_keys() {
     assert_eq!(cfg.list_margin, -1);
     assert_eq!(cfg.links_space_char, " ");
     assert!(!cfg.auto_toc);
+    assert!(!cfg.auto_generate_links);
+    assert!(!cfg.auto_generate_tags);
+    assert!(!cfg.auto_diary_index);
     // Generated-section captions match upstream defaults.
     assert_eq!(cfg.toc_header, "Contents");
     assert_eq!(cfg.toc_header_level, 1);
@@ -301,6 +304,9 @@ fn raw_wiki_parses_every_new_key() {
             "list_margin": 2,
             "links_space_char": "_",
             "auto_toc": true,
+            "auto_generate_links": true,
+            "auto_generate_tags": 1,
+            "auto_diary_index": true,
             "toc_header": "Table of Contents",
             "toc_header_level": 2,
             "links_header": "All Pages",
@@ -323,6 +329,9 @@ fn raw_wiki_parses_every_new_key() {
     assert_eq!(w.list_margin, 2);
     assert_eq!(w.links_space_char, "_");
     assert!(w.auto_toc);
+    assert!(w.auto_generate_links);
+    assert!(w.auto_generate_tags); // int 1 → true
+    assert!(w.auto_diary_index);
     assert_eq!(w.toc_header, "Table of Contents");
     assert_eq!(w.toc_header_level, 2);
     assert_eq!(w.links_header, "All Pages");