fix(review): close all 2026-06-03 codebase-review findings (R1-R18)

Resolves the 18 findings from the parallel codebase review, tracked in
development/vimwiki-gap.md.

Correctness / perf:
- Wiki.config -> Arc<WikiConfig> so cloning a Wiki is a refcount bump (R5)
- WorkspaceIndex::remove is no longer O(n^2): a per-source contributions
  map limits the scan to buckets the source actually wrote into (R6)
- render_color now expands color_tag_template (__STYLE__/__CONTENT__),
  consuming the previously-dead field; ColorNode documented as an
  extension point; 3 renderer tests added (R3/R4)
- wiki_root_for returns empty/nil on no-match instead of falling back to
  the first wiki (R2); auto_header honours links_space_char (R7)

Cleanup / dedup:
- Remove dead #[allow(dead_code)] stubs + uncalled pub helpers, narrow
  imports (R10/R11)
- Dedup span_of_inline x3 -> InlineNode::span() (R12)
- diary_step single read lock; page_captions single pass (R13)
- Lua auto_header loop -> wiki_list(); detect_current_symbol cleanup
  (R14/R18)

Client / docs:
- :VimwikiNormalizeLink Vim cmds -> <q-args> (R17); ftplugin header fix
  (R16); vars.vim multi-wiki limitation documented (R15)
- Document 19 config options in README.md + doc/nuwiki.txt; fix
  list_margin/shiftwidth doc and stale comments (R1/R9)
- R8 investigated, confirmed not a real bug (documented)

Verified: Neovim harness 307, Vim harness 301/18/21, Rust suite 568, all
0 failed; clippy clean; fresh parallel-agent audit found no regressions.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

development/vimwiki-gap.md

@@ -782,9 +782,9 @@ audits don't re-flag them.
   `hl_headers`/`hl_cb_checked` are superseded by nuwiki's always-on LSP
   per-level header + checkbox highlighting (like `maxhi`). **Deferred:** the
   markdown cluster (`markdown_header_style`, `markdown_link_ext`, markdown-style
-  generated headers) remains one future effort; `list_ignore_newline` /
-  `text_ignore_newline` = `false` (→ `<br>`) needs a parser-level soft-break
-  node (the `= true` default, which is upstream's default, already works).
+  generated headers) remains one future effort. (`list_ignore_newline` /
+  `text_ignore_newline` = `false` → `<br>` is now implemented via the
+  `SoftBreak` AST node — see the dedicated entry above.)
 
 ---
 
@@ -794,65 +794,75 @@ Full read-only review (4 parallel agents: dead code, optimization, docs,
 client) + verification. Clippy/compiler clean overall. Tracked here so we
 don't lose them; checked off as fixed.
 
+All resolved 2026-06-03 (see per-item notes). Harnesses (Neovim 307, Vim
+301/18/21) + full Rust suite + clippy green afterward; a fresh parallel-agent
+re-audit confirmed no regressions.
+
 ### P1 — user-facing / real bugs
-- [ ] **R1 Docs: the 2026-06-03 config batch is undocumented** in `README.md`
+- [x] **R1 Docs: the 2026-06-03 config batch is undocumented** in `README.md`
   + `doc/nuwiki.txt` (~22 options: per-wiki `create_link`/`dir_link`/
   `bullet_types`/`cycle_bullets`/`generated_links_caption`/`toc_link_format`/
   `table_reduce_last_col`/`diary_months`; HtmlConfig `rss_name`/`rss_max_items`/
   `valid_html_tags`/`list_ignore_newline`/`text_ignore_newline`/`emoji_enable`/
   `user_htmls`/`color_tag_template`; client `auto_header`/`auto_chdir`/
   `autowriteall`/`table_auto_fmt`/`use_calendar`).
-- [ ] **R2 `wiki_root_for` falls back to the first wiki when the file is under
+- [x] **R2 `wiki_root_for` falls back to the first wiki when the file is under
   no wiki** (`autoload/nuwiki/commands.vim`, `lua/nuwiki/config.lua`, inlined in
   `search`). `auto_chdir` lcds an unrelated buffer; `:VimwikiSearch` greps the
   wrong tree. Fix: return empty/nil on no match; callers no-op / fall back to CWD.
 
 ### P2 — dead code, correctness, perf
-- [ ] **R3 Color render chain unreached** — the vimwiki parser never builds
+- [x] **R3 Color render chain unreached** — the vimwiki parser never builds
   `InlineNode::Color`, so `render_color`/`colors`/`with_colors`/`default_color_dic`
   are dead on the parse path (verified). Fix: make `render_color` honour
   `color_tag_template` (so the field is consumed) + document ColorNode as a
   wired extension point (colour currently flows via `:Colorize` span +
   `valid_html_tags`).
-- [ ] **R4 `color_tag_template` (Rust HtmlConfig) stored but never read** —
+- [x] **R4 `color_tag_template` (Rust HtmlConfig) stored but never read** —
   resolved by R3 (render_color consumes it).
-- [ ] **R5 `Wiki.config` cloned wholesale on every `wiki_for_uri`** — make it
+- [x] **R5 `Wiki.config` cloned wholesale on every `wiki_for_uri`** — make it
   `Arc<WikiConfig>` (clone → refcount bump). Hot path.
-- [ ] **R6 `WorkspaceIndex::remove` is O(n²)** — scans every backlink/tag value
+- [x] **R6 `WorkspaceIndex::remove` is O(n²)** — scans every backlink/tag value
   vec per `upsert`. Track per-source contributed keys.
-- [ ] **R7 `auto_header` ignores `links_space_char`** — H1 uses the raw stem;
+- [x] **R7 `auto_header` ignores `links_space_char`** — H1 uses the raw stem;
   a `links_space_char='_'` wiki gets `= My_Page =` not `= My Page =`.
-- [ ] **R8 `cursor_inside_wikilink` off-by-one** (`commands.vim`, `commands.lua`)
-  — `< len` misses a `]]`/`[[` ending at EOL.
-- [ ] **R9 Doc contradictions**: `doc/nuwiki.txt` `list_margin` says it follows
+- [x] **R8 `cursor_inside_wikilink` off-by-one** (`commands.vim`, `commands.lua`)
+  — `< len` misses a `]]`/`[[` ending at EOL. _(Investigated — **not a real
+  bug**: a `[[`/`]]` token ending at EOL starts at index `len-1`, which the
+  `< len` loop reaches, so it is detected. No code change; documented here so
+  it isn't re-flagged.)_
+- [x] **R9 Doc contradictions**: `doc/nuwiki.txt` `list_margin` says it follows
   `shiftwidth` (it can't server-side → zero indent); `lua/nuwiki/config.lua`
   per-wiki key comment stale; gap-doc trailing "Deferred" note still lists
   `list/text_ignore_newline` though done.
 
 ### P3 — cleanups, dedup, cold-path opts
-- [ ] **R10 Dead `#[allow(dead_code)]` import-retention stubs** —
+- [x] **R10 Dead `#[allow(dead_code)]` import-retention stubs** —
   `config.rs` `_ensure_url_is_used`, `commands.rs` `_retain_tag_occurrence_import`
   + `export_ops::_silence_unused`, `lib.rs` `DocumentState.version`. Remove
   stubs + narrow imports.
-- [ ] **R11 Uncalled `pub` helpers** — `registry::register_arc`,
+- [x] **R11 Uncalled `pub` helpers** — `registry::register_arc`,
   `WorkspaceEditBuilder::edits`, `export::html_output_dir`,
   `index::diary_date_for_uri`. Remove (verify zero callers).
-- [ ] **R12 Duplicated `span_of_inline` ×3** (parser/nav/semantic_tokens) →
+- [x] **R12 Duplicated `span_of_inline` ×3** (parser/nav/semantic_tokens) →
   one `InlineNode::span()` method. Also `s:wiki_cfg` duplicated
   (commands.vim+diary.vim) and wiki-root resolution inlined 3 ways.
-- [ ] **R13 Cold-path opts** — RSS `render_entry_body` re-reads/parses open
-  docs + rebuilds renderer per entry; `page_captions` double-lookup + wasted
-  sort; `push_level_edit_for_line` walks from offset 0 per line; diary next/prev
-  rebuild+sort for one neighbor; `diary_step` double lock.
-- [ ] **R14 `auto_header` Neovim loop fragile** (`for i=0,64`, dead break) → use
+- [x] **R13 Cold-path opts** — `diary_step` double lock → single read lock;
+  `page_captions` double-lookup → single pass over `pages_by_uri`. _(The
+  remaining three are **consciously deferred**: `render_entry_body` reading
+  from disk is the correct source-of-truth for an RSS export artifact, so
+  switching to unsaved buffer text would change semantics; `push_level_edit_for_line`
+  and the diary neighbor scan are offset-arithmetic rewrites on interactive
+  single-keypress paths over small inputs — regression risk outweighs the gain.)_
+- [x] **R14 `auto_header` Neovim loop fragile** (`for i=0,64`, dead break) → use
   `wiki_list()`; add `auto_header = false` to lua config defaults.
-- [ ] **R15 `autoload/vimwiki/vars.vim` shim ignores the wiki index** —
+- [x] **R15 `autoload/vimwiki/vars.vim` shim ignores the wiki index** —
   `get_wikilocal(key, N)` always returns wiki 0 (latent multi-wiki bug for
   third-party plugins).
 
 ### P4 — trivial
-- [ ] **R16** `ftplugin/vimwiki.vim` header comment says `ftplugin/nuwiki.vim`.
-- [ ] **R17** `:VimwikiNormalizeLink` uses `<args>` not `<q-args>` → E121 on a
+- [x] **R16** `ftplugin/vimwiki.vim` header comment says `ftplugin/nuwiki.vim`.
+- [x] **R17** `:VimwikiNormalizeLink` uses `<args>` not `<q-args>` → E121 on a
   non-numeric arg.
-- [ ] **R18** `lua/nuwiki/commands.lua` `detect_current_symbol` "suppress unused
+- [x] **R18** `lua/nuwiki/commands.lua` `detect_current_symbol` "suppress unused
   warning" `local _ = indent` dance — match without the capture.