feat(config): P3 config batch — group 7 (user_htmls pruning)

allToHtml now prunes orphan HTML files (no corresponding wiki source) under
html_path — export_ops::prune_orphan_html walks the output tree, maps each
<rel>.html back to <root>/<rel>.<ext>, and deletes those with no source,
skipping the CSS file and any basename in user_htmls. Gated on
!html_filename_parameterization (slugified names can't be reverse-mapped),
mirroring upstream; the pruned paths are reported in the command result.

hl_headers / hl_cb_checked are NOT implemented as toggles: nuwiki already
highlights headers per-level (@vimwikiHeading.level1..6) and checkboxes
always-on via LSP semantic tokens, which supersedes the upstream opt-in
toggles (default off) — same class as the maxhi divergence. Documented in the
gap doc rather than degrading the existing highlighting.

Test: prune_orphan_html_deletes_sourceless_keeps_protected. Full rust suite +
clippy clean.

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

crates/nuwiki-lsp/tests/html_export.rs

@@ -631,6 +631,32 @@ fn write_rss_uses_base_url_for_public_links() {
     assert!(!xml.contains("file:///tmp/diary"));
 }
 
+#[test]
+fn prune_orphan_html_deletes_sourceless_keeps_protected() {
+    let root = temp_root("prune");
+    let mut c = WikiConfig::from_root(root.clone());
+    c.html = HtmlConfig::from_root(&root);
+    c.html.user_htmls = vec!["keep.html".into()];
+    let html = &c.html.html_path;
+    std::fs::create_dir_all(html).unwrap();
+    // A sourced page (Home.wiki exists) → kept.
+    std::fs::write(root.join("Home.wiki"), "= Home =\n").unwrap();
+    std::fs::write(html.join("Home.html"), "<h1>Home</h1>").unwrap();
+    // An orphan (no source) → pruned.
+    std::fs::write(html.join("Ghost.html"), "<h1>Ghost</h1>").unwrap();
+    // A user_htmls-protected orphan → kept.
+    std::fs::write(html.join("keep.html"), "<p>manual</p>").unwrap();
+    // The CSS file → never pruned.
+    std::fs::write(html.join(&c.html.css_name), "body{}").unwrap();
+
+    let pruned = nuwiki_lsp::commands::export_ops::prune_orphan_html(&c);
+    assert_eq!(pruned.len(), 1, "only the orphan: {pruned:?}");
+    assert!(!html.join("Ghost.html").exists(), "orphan deleted");
+    assert!(html.join("Home.html").exists(), "sourced kept");
+    assert!(html.join("keep.html").exists(), "user_htmls kept");
+    assert!(html.join(&c.html.css_name).exists(), "css kept");
+}
+
 #[test]
 fn write_rss_honours_rss_name_and_max_items() {
     use nuwiki_lsp::diary::DiaryEntry;