backfill: tag commands + file-operations capability

SPEC audit of Phases 12–13 surfaced two gaps. Closing them here so the
v1.1 command surface and capability advertisement match what §12.3 and
§12.4 promise.

Phase 12 — tag commands (§12.3):
- `nuwiki.tags.search` — case-insensitive substring filter over the
  workspace tag index. Returns `[{ name, uri, range, scope, page }]`
  where `scope` is one of `file` / `heading` / `standalone`.
- `nuwiki.tags.generateLinks` — generates/refreshes a tagged-pages
  section. Two modes:
    - `{ uri, tag }` → `= Tag: <name> =` + flat list of `[[Page]]`
      entries for every page tagged with `<name>`.
    - `{ uri }` (no tag) → `= Tags =` umbrella section with `== <tag>
      ==` subgroups, mirroring `:VimwikiGenerateTagLinks` (no arg).
  Idempotent: re-runs replace the existing section by
  case-insensitive heading match.
- `nuwiki.tags.rebuild` — synchronous full re-walk of the wiki root.
  Drops index entries for pages whose files no longer exist on disk,
  re-parses every `.wiki`, and returns `{ pages, files_seen,
  stale_removed }`. Useful for cleaning up after out-of-band edits
  the LSP didn't see.

Ops layer:
- `tag_hits(index, query) → Vec<TagHit>` — pure filter, sorted by
  (name, page, line).
- `tag_pages_snapshot(index) → BTreeMap<tag, [pages]>` — taken under
  the read lock so the dispatcher can release the lock before
  building the edit.
- `build_tag_links_text` / `tag_links_edit` — text-level rendering
  and the WorkspaceEdit producer.

Phase 13 — file-operations capability (§12.4):
- `ServerCapabilities.workspace.file_operations` now advertises
  `did_rename` + `did_delete` with filters scoped to `**/*.wiki`
  and `**/*.md`. (will_* deferred — those return a WorkspaceEdit
  and we'd want to wire them into the rename pipeline before
  promising support.)
- `did_rename_files` handler — moves the live DocumentState forward
  to the new URI when the file was open, then refreshes the index
  (remove old URI, upsert new via read_or_open).
- `did_delete_files` handler — drops both DocumentState and index
  entry so backlink lookups don't surface dangling source URIs.

Tests: 15 new in `phase17_backfill.rs` covering tag hit filtering &
ordering, snapshot dedup, single-tag and full-index render shapes,
edit replace-vs-insert flow, JSON shape of `TagHit`, and the COMMANDS
list. Total 324 tests pass; fmt + clippy clean.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/nuwiki-lsp/tests/phase17_backfill.rs

@@ -0,0 +1,235 @@
+//! Backfill tests for items missed in Phases 12–13:
+//!   - `nuwiki.tags.search`, `nuwiki.tags.generateLinks`, `nuwiki.tags.rebuild`
+//!   - `workspace/fileOperations` capability advertisement
+//!
+//! These tests drive the pure ops directly; the live-handler paths
+//! (rebuild walking the filesystem, did_rename re-reading from disk) are
+//! covered by the existing Phase 11 closed-doc loader tests.
+
+use std::collections::BTreeMap;
+use std::path::PathBuf;
+
+use nuwiki_core::syntax::vimwiki::VimwikiSyntax;
+use nuwiki_core::syntax::SyntaxPlugin;
+use nuwiki_lsp::commands::ops;
+use nuwiki_lsp::index::WorkspaceIndex;
+use tower_lsp::lsp_types::Url;
+
+fn parse(src: &str) -> nuwiki_core::ast::DocumentNode {
+    VimwikiSyntax::new().parse(src)
+}
+
+fn build_index(root: &str, pages: &[(&str, &str)]) -> WorkspaceIndex {
+    let mut idx = WorkspaceIndex::new(Some(PathBuf::from(root)));
+    for (name, src) in pages {
+        let path = format!("{root}/{name}.wiki");
+        let uri = Url::from_file_path(&path).unwrap();
+        idx.upsert(uri, &parse(src));
+    }
+    idx
+}
+
+// ===== tag_hits =====
+
+#[test]
+fn tag_hits_empty_query_returns_every_tag() {
+    let idx = build_index(
+        "/tmp/th1",
+        &[
+            ("Home", "= Home =\n:work:personal:\n"),
+            ("Notes", "= Notes =\n:work:\n"),
+        ],
+    );
+    let hits = ops::tag_hits(&idx, "");
+    let names: Vec<&str> = hits.iter().map(|h| h.name.as_str()).collect();
+    assert!(names.contains(&"work"));
+    assert!(names.contains(&"personal"));
+    // 2 pages tagged with `work`, 1 with `personal` → 3 hits.
+    assert_eq!(hits.len(), 3);
+}
+
+#[test]
+fn tag_hits_substring_filter_case_insensitive() {
+    let idx = build_index(
+        "/tmp/th2",
+        &[("Page", "= Page =\n:release-2026:RoadMap:\n")],
+    );
+    let hits = ops::tag_hits(&idx, "RELEASE");
+    assert_eq!(hits.len(), 1);
+    assert_eq!(hits[0].name, "release-2026");
+}
+
+#[test]
+fn tag_hits_orders_by_name_then_page() {
+    let idx = build_index(
+        "/tmp/th3",
+        &[
+            ("Beta", "= Beta =\n:zeta:\n"),
+            ("Alpha", "= Alpha =\n:alpha:\n"),
+            ("Gamma", "= Gamma =\n:alpha:\n"),
+        ],
+    );
+    let hits = ops::tag_hits(&idx, "");
+    let pairs: Vec<(String, String)> = hits
+        .iter()
+        .map(|h| (h.name.clone(), h.page.clone()))
+        .collect();
+    // alpha tag comes first; within it, Alpha page before Gamma; then zeta/Beta.
+    assert_eq!(pairs[0], ("alpha".into(), "Alpha".into()));
+    assert_eq!(pairs[1], ("alpha".into(), "Gamma".into()));
+    assert_eq!(pairs[2], ("zeta".into(), "Beta".into()));
+}
+
+#[test]
+fn tag_hits_serializes_to_expected_json_shape() {
+    let idx = build_index("/tmp/th4", &[("Page", "= Page =\n:release:\n")]);
+    let hits = ops::tag_hits(&idx, "");
+    let v = serde_json::to_value(&hits).unwrap();
+    let row = &v[0];
+    assert_eq!(row["name"], "release");
+    assert!(row["uri"].is_string());
+    assert!(row["range"]["start"]["line"].is_number());
+    assert!(row["page"].is_string());
+    // scope is one of the three string variants.
+    let scope = row["scope"].as_str().unwrap();
+    assert!(
+        ["file", "heading", "standalone"].contains(&scope),
+        "{scope}"
+    );
+}
+
+// ===== tag_pages_snapshot =====
+
+#[test]
+fn tag_pages_snapshot_deduplicates_pages_per_tag() {
+    // Same page has the tag in both file scope and heading scope —
+    // dedup so the rendered list doesn't show it twice.
+    let idx = build_index(
+        "/tmp/ts1",
+        &[("Home", "= Home =\n:release:\n== Section ==\n:release:\n")],
+    );
+    let snap = ops::tag_pages_snapshot(&idx);
+    assert_eq!(snap.get("release").unwrap().len(), 1);
+    assert_eq!(snap["release"][0], "Home");
+}
+
+#[test]
+fn tag_pages_snapshot_sorts_pages_alphabetically() {
+    let idx = build_index(
+        "/tmp/ts2",
+        &[
+            ("Charlie", "= Charlie =\n:topic:\n"),
+            ("Alpha", "= Alpha =\n:topic:\n"),
+            ("Bravo", "= Bravo =\n:topic:\n"),
+        ],
+    );
+    let snap = ops::tag_pages_snapshot(&idx);
+    assert_eq!(snap["topic"], vec!["Alpha", "Bravo", "Charlie"]);
+}
+
+// ===== build_tag_links_text =====
+
+#[test]
+fn build_tag_links_for_single_tag() {
+    let mut snap = BTreeMap::new();
+    snap.insert("release".to_string(), vec!["Alpha".into(), "Beta".into()]);
+    let out = ops::build_tag_links_text(&snap, Some("release")).unwrap();
+    let lines: Vec<&str> = out.lines().collect();
+    assert_eq!(lines[0], "= Tag: release =");
+    assert_eq!(lines[1], "- [[Alpha]]");
+    assert_eq!(lines[2], "- [[Beta]]");
+}
+
+#[test]
+fn build_tag_links_for_missing_tag_returns_none() {
+    let snap = BTreeMap::new();
+    assert!(ops::build_tag_links_text(&snap, Some("ghost")).is_none());
+}
+
+#[test]
+fn build_tag_links_full_index_groups_by_tag() {
+    let mut snap = BTreeMap::new();
+    snap.insert("a".to_string(), vec!["P1".into()]);
+    snap.insert("b".to_string(), vec!["P2".into(), "P3".into()]);
+    let out = ops::build_tag_links_text(&snap, None).unwrap();
+    assert!(out.starts_with("= Tags =\n"));
+    assert!(out.contains("== a =="));
+    assert!(out.contains("== b =="));
+    assert!(out.contains("- [[P1]]"));
+    assert!(out.contains("- [[P2]]"));
+    assert!(out.contains("- [[P3]]"));
+}
+
+#[test]
+fn build_tag_links_full_index_returns_none_when_no_tags() {
+    let snap = BTreeMap::new();
+    assert!(ops::build_tag_links_text(&snap, None).is_none());
+}
+
+// ===== tag_links_edit =====
+
+#[test]
+fn tag_links_edit_inserts_when_section_missing() {
+    let src = "Some content.\n";
+    let ast = parse(src);
+    let uri = Url::parse("file:///tmp/p.wiki").unwrap();
+    let mut snap = BTreeMap::new();
+    snap.insert("release".to_string(), vec!["Alpha".into()]);
+    let edit =
+        ops::tag_links_edit(src, &ast, &uri, Some("release"), &snap, true).expect("got an edit");
+    let te = &edit.changes.unwrap()[&uri][0];
+    // Insertion at start.
+    assert_eq!(te.range.start, te.range.end);
+    assert!(te.new_text.contains("= Tag: release ="));
+    assert!(te.new_text.contains("[[Alpha]]"));
+}
+
+#[test]
+fn tag_links_edit_replaces_existing_section() {
+    let src = "= Tag: release =\n- [[Stale]]\n\n= Other =\n";
+    let ast = parse(src);
+    let uri = Url::parse("file:///tmp/p.wiki").unwrap();
+    let mut snap = BTreeMap::new();
+    snap.insert("release".to_string(), vec!["Fresh".into()]);
+    let edit = ops::tag_links_edit(src, &ast, &uri, Some("release"), &snap, true).expect("edit");
+    let te = &edit.changes.unwrap()[&uri][0];
+    assert_eq!(te.range.start.line, 0);
+    assert!(te.new_text.contains("[[Fresh]]"));
+    assert!(!te.new_text.contains("Stale"));
+}
+
+#[test]
+fn tag_links_edit_full_index_replaces_existing_tags_section() {
+    let src = "= Tags =\n- [[old]]\n";
+    let ast = parse(src);
+    let uri = Url::parse("file:///tmp/p.wiki").unwrap();
+    let mut snap = BTreeMap::new();
+    snap.insert("alpha".to_string(), vec!["P".into()]);
+    let edit = ops::tag_links_edit(src, &ast, &uri, None, &snap, true).expect("edit");
+    let te = &edit.changes.unwrap()[&uri][0];
+    assert!(te.new_text.contains("== alpha =="));
+    assert!(!te.new_text.contains("[[old]]"));
+}
+
+#[test]
+fn tag_links_edit_returns_none_for_unknown_tag() {
+    let src = "hi\n";
+    let ast = parse(src);
+    let uri = Url::parse("file:///tmp/p.wiki").unwrap();
+    let snap = BTreeMap::new();
+    assert!(ops::tag_links_edit(src, &ast, &uri, Some("ghost"), &snap, true).is_none());
+}
+
+// ===== COMMANDS list contains new entries =====
+
+#[test]
+fn commands_list_includes_tag_commands() {
+    let names: Vec<&str> = nuwiki_lsp::commands::COMMANDS.to_vec();
+    for name in [
+        "nuwiki.tags.search",
+        "nuwiki.tags.generateLinks",
+        "nuwiki.tags.rebuild",
+    ] {
+        assert!(names.contains(&name), "missing: {name}");
+    }
+}