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/src/lib.rs

@@ -42,18 +42,21 @@ use tokio::io::{AsyncRead, AsyncWrite};
 use tower_lsp::jsonrpc::Result as LspResult;
 use tower_lsp::lsp_types::{
     CompletionItem, CompletionItemKind, CompletionOptions, CompletionParams, CompletionResponse,
-    Diagnostic, DiagnosticSeverity, DidChangeConfigurationParams, DidChangeTextDocumentParams,
-    DidCloseTextDocumentParams, DidOpenTextDocumentParams, DocumentSymbol, DocumentSymbolParams,
-    DocumentSymbolResponse, ExecuteCommandOptions, ExecuteCommandParams, GotoDefinitionParams,
-    GotoDefinitionResponse, Hover, HoverContents, HoverParams, HoverProviderCapability,
-    InitializeParams, InitializeResult, InitializedParams, Location, MarkupContent, MarkupKind,
-    MessageType, OneOf, PositionEncodingKind, ProgressParams, ProgressParamsValue, ProgressToken,
-    Range, ReferenceParams, RenameParams, SemanticTokens, SemanticTokensFullOptions,
+    DeleteFilesParams, Diagnostic, DiagnosticSeverity, DidChangeConfigurationParams,
+    DidChangeTextDocumentParams, DidCloseTextDocumentParams, DidOpenTextDocumentParams,
+    DocumentSymbol, DocumentSymbolParams, DocumentSymbolResponse, ExecuteCommandOptions,
+    ExecuteCommandParams, FileOperationFilter, FileOperationPattern, FileOperationPatternKind,
+    FileOperationRegistrationOptions, GotoDefinitionParams, GotoDefinitionResponse, Hover,
+    HoverContents, HoverParams, HoverProviderCapability, InitializeParams, InitializeResult,
+    InitializedParams, Location, MarkupContent, MarkupKind, MessageType, OneOf,
+    PositionEncodingKind, ProgressParams, ProgressParamsValue, ProgressToken, Range,
+    ReferenceParams, RenameFilesParams, RenameParams, SemanticTokens, SemanticTokensFullOptions,
     SemanticTokensOptions, SemanticTokensParams, SemanticTokensRangeParams,
     SemanticTokensRangeResult, SemanticTokensResult, SemanticTokensServerCapabilities,
     ServerCapabilities, ServerInfo, SymbolInformation as LspSymbolInformation, SymbolKind,
     TextDocumentSyncCapability, TextDocumentSyncKind, Url, WorkDoneProgress, WorkDoneProgressBegin,
-    WorkDoneProgressEnd, WorkDoneProgressOptions, WorkspaceEdit, WorkspaceSymbolParams,
+    WorkDoneProgressEnd, WorkDoneProgressOptions, WorkspaceEdit,
+    WorkspaceFileOperationsServerCapabilities, WorkspaceServerCapabilities, WorkspaceSymbolParams,
 };
 use tower_lsp::{Client, LanguageServer, LspService, Server};
 
@@ -320,6 +323,10 @@ impl LanguageServer for Backend {
                         },
                     ),
                 ),
+                workspace: Some(WorkspaceServerCapabilities {
+                    workspace_folders: None,
+                    file_operations: Some(wiki_file_operations()),
+                }),
                 ..ServerCapabilities::default()
             },
             server_info: Some(ServerInfo {
@@ -387,6 +394,52 @@ impl LanguageServer for Backend {
         }
     }
 
+    async fn did_rename_files(&self, params: RenameFilesParams) {
+        // Phase 13 advertises this capability so the editor pushes
+        // out-of-band renames (file explorer drags, `:VimwikiRenameFile`
+        // when the client opts to surface the new URI). Update the index
+        // so backlinks/headings track the new URI without waiting for
+        // didOpen on the renamed buffer.
+        for fr in &params.files {
+            let Ok(old_uri) = Url::parse(&fr.old_uri) else {
+                continue;
+            };
+            let Ok(new_uri) = Url::parse(&fr.new_uri) else {
+                continue;
+            };
+            // Pull the live document forward if it was open under the old
+            // URI. Otherwise read the new path from disk and parse.
+            if let Some((_, state)) = self.documents.remove(&old_uri) {
+                self.documents.insert(new_uri.clone(), state);
+            }
+            if let Some(wiki) = self.wiki_for_uri(&new_uri) {
+                let mut idx = wiki.index.write().expect("index lock poisoned");
+                idx.remove(&old_uri);
+            }
+            if let Ok(snapshot) = self.read_or_open(&new_uri).await {
+                if let Some(wiki) = self.wiki_for_uri(&new_uri) {
+                    let mut idx = wiki.index.write().expect("index lock poisoned");
+                    idx.upsert(new_uri.clone(), &snapshot.ast);
+                }
+            }
+        }
+    }
+
+    async fn did_delete_files(&self, params: DeleteFilesParams) {
+        // Mirror of did_rename: drop the index entry so backlink lookups
+        // stop returning the now-missing source URI.
+        for f in &params.files {
+            let Ok(uri) = Url::parse(&f.uri) else {
+                continue;
+            };
+            self.documents.remove(&uri);
+            if let Some(wiki) = self.wiki_for_uri(&uri) {
+                let mut idx = wiki.index.write().expect("index lock poisoned");
+                idx.remove(&uri);
+            }
+        }
+    }
+
     async fn did_close(&self, params: DidCloseTextDocumentParams) {
         let uri = &params.text_document.uri;
         self.documents.remove(uri);
@@ -713,6 +766,43 @@ impl LanguageServer for Backend {
     }
 }
 
+/// File-operation capability for `.wiki` files. Tells the client to
+/// notify us before/after the user renames or deletes files via the file
+/// explorer (or any other out-of-buffer trigger). Filters scope these
+/// notifications to wiki sources so we don't see every C++ rename in a
+/// polyglot workspace.
+fn wiki_file_operations() -> WorkspaceFileOperationsServerCapabilities {
+    let filters = vec![
+        FileOperationFilter {
+            scheme: Some("file".into()),
+            pattern: FileOperationPattern {
+                glob: "**/*.wiki".into(),
+                matches: Some(FileOperationPatternKind::File),
+                options: None,
+            },
+        },
+        FileOperationFilter {
+            scheme: Some("file".into()),
+            pattern: FileOperationPattern {
+                glob: "**/*.md".into(),
+                matches: Some(FileOperationPatternKind::File),
+                options: None,
+            },
+        },
+    ];
+    let opts = || FileOperationRegistrationOptions {
+        filters: filters.clone(),
+    };
+    WorkspaceFileOperationsServerCapabilities {
+        did_create: None,
+        will_create: None,
+        did_rename: Some(opts()),
+        will_rename: None,
+        did_delete: Some(opts()),
+        will_delete: None,
+    }
+}
+
 fn pack_data(flat: &[u32]) -> Vec<tower_lsp::lsp_types::SemanticToken> {
     flat.chunks_exact(5)
         .map(|c| tower_lsp::lsp_types::SemanticToken {