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>

development/vimwiki-gap.md

@@ -98,9 +98,18 @@ fix site.
   auto_toc save hook) and `find_section_range` matches the configured text so
   regen stays idempotent. Tests: `captions_honour_custom_header_and_level`
   (`link_health.rs`) + config round-trip in `index_and_config.rs`.
-- [ ] **On-save autoregen family** — `auto_diary_index`, `auto_generate_links`,
-  `auto_generate_tags`, `auto_tags` (only `auto_toc` / `auto_export` exist).
-  _Fix:_ `config.rs` `RawWiki`/`WikiConfig` + the `didSave` path.
+- [x] **On-save autoregen family** — added per-wiki `auto_generate_links`,
+  `auto_generate_tags`, `auto_diary_index` (all default `false`, like upstream),
+  wired into the `did_save` hook (`crates/nuwiki-lsp/src/lib.rs`) mirroring
+  `auto_toc`: regen runs only when the section already exists
+  (`links_rebuild_edit` / `tag_links_rebuild_edit`), and `auto_diary_index`
+  regenerates the diary index when a dated diary *entry* is saved
+  (`diary_generate_index_edit`, which handles an open/closed/absent index file).
+  `auto_tags` is an **intentional divergence** (see below): nuwiki re-indexes on
+  every change, so tag metadata is always fresh — there's no on-disk metadata
+  file to update on save. Tests: `links_rebuild_edit_only_acts_when_section_present`
+  (`link_health.rs`), `tag_links_rebuild_edit_only_acts_when_index_present`
+  (`commands_tags.rs`), config round-trip + defaults (`index_and_config.rs`).
 - [x] **`listsym_rejected`** — the rejected glyph was a hardcoded `const '-'`.
   _Fix:_ `ListSyms` gained a `rejected` field + `new_with_rejected()`
   (`crates/nuwiki-core/src/listsyms.rs`); per-wiki `listsym_rejected` key (default
@@ -276,6 +285,11 @@ audits don't re-flag them.
 - `key_mappings` (dict) — replaced by Lua `mappings.<group>` + the
   `g:nuwiki_no_<group>_mappings` globals.
 - `use_calendar` — no calendar.vim integration.
+- `auto_tags` (upstream `0`) — upstream auto-updates an on-disk tag *metadata*
+  file on save. nuwiki has no such file: the LSP re-indexes tags on every
+  `didChange`, so tag search/jump/completion are always fresh. The setting's
+  intent is therefore always satisfied (the `auto_generate_tags` regen of the
+  in-buffer links section is the configurable on-save piece).
 - Mouse maps (`<2-LeftMouse>`, `<MiddleMouse>`, …) — upstream binds them
   unconditionally; nuwiki ships them **opt-in** (`mappings.mouse` /
   `g:nuwiki_mouse_mappings`). Deliberate, so they're not always-on.