feat(mcp): search_in_page tool — in-page substring/regex search for the agent (#330)

Editorial roles (Corrector/Factchecker) brute-forced `get_node` block-by-block to
find occurrences (unquoted «ё», straight quotes, «т.е.»), burning tokens. New
`search_in_page(pageId, query, {regex?, caseSensitive?, limit?})` reads the page's
ProseMirror JSON via the existing getPageRaw and searches it IN MEMORY — no server
endpoint, no DB/schema change, no touch to the packages/mcp/src/lib schema mirror.

New pure `searchInDoc(doc, query, opts)` (packages/mcp/src/lib/page-search.ts):
recursive descent to each TEXT CONTAINER (paragraph/heading/table-cell paragraph),
glues its inline text via `blockPlainText` (a match survives inline-mark
boundaries — e.g. «т.е.» split across bold/italic), searches literal (indexOf) or
regex, and returns `{ total, truncated, matches:[{ nodeId, blockIndex, type,
before, match, after }] }`. `nodeId` is the container's attrs.id or the
`#<topLevelIndex>` of the enclosing top-level block — the SAME ref format
get_node/patch_node/comment-anchoring accept (verified identical to getNodeByRef),
so the agent goes straight from a hit to a targeted comment; `before`/`after` are
~40-char windows for a unique selection. `total`/`truncated` always reported (never
silent truncation). Lives in the SHARED_TOOL_SPECS registry → exposed in BOTH
transports (external /mcp + in-app AI-chat), with a SERVER_INSTRUCTIONS line and a
DocmostClientLike signature + contract-test entry. Corrector/Factchecker prompts
get a one-line "use search_in_page first" hint (versions bumped, catalog hash lock
refreshed).

Guards: empty/whitespace query → clear error; invalid regex → clear error (not a
generic 500); zero-length regex matches (`\b`, `a*`) skipped with lastIndex
advanced (no loop/flood); MAX_PATTERN_LENGTH=1000, MAX_CONTAINER_TEXT=100k bound
each exec; limit clamped [1,200] (default 50).

Tests: new page-search.test.mjs (17) — literal+regex, case-sensitivity,
mark-boundary glue, nodeId for paragraph/heading (attrs.id) and table-cell
(#<index> fallback), context bounds, limit/total/truncated + clamp, invalid
regex/empty/over-long errors, zero-length skip, empty-doc null-safety.

mcp: tsc clean; node --test 467 passed (+17). apps/server: tsc --noEmit clean
(DocmostClientLike + wiring). catalog check.mjs OK.

Known limitations (from internal review, non-blocking):
- Residual ReDoS: a crafted catastrophic-backtracking pattern (e.g. `(a+)+$`)
  against a large single container can hang the event loop — JS regex is not
  interruptible, so the length caps bound the base but not the backtracking.
  Realistic exposure is low (containers are small; the pattern is supplied by the
  authenticated model). Candidate for a follow-up hardening (safe-regex validation
  or a worker+timeout) if it matters.
- Case-insensitive LITERAL search folds via toLowerCase; a char whose lowercase
  differs in length (e.g. Turkish İ) BEFORE a match could shift the context
  window — negligible for the RU/EN editorial scenario.
- On a `#<index>` table-cell fallback, `type` is the inline container ("paragraph")
  while nodeId addresses the top-level block — addressing is correct; the field is
  documented as the container's type.

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

apps/server/src/core/ai-chat/tools/ai-chat-tools.service.ts

@@ -630,6 +630,16 @@ export class AiChatToolsService {
         async ({ pageId, nodeId }) => await client.getNode(pageId, nodeId),
       ),
 
+      searchInPage: sharedTool(
+        sharedToolSpecs.searchInPage,
+        async ({ pageId, query, regex, caseSensitive, limit }) =>
+          await client.searchInPage(pageId, query, {
+            regex,
+            caseSensitive,
+            limit,
+          }),
+      ),
+
       getTable: tool({
         description:
           'Read a table as a matrix of cell texts (plus a parallel cellIds ' +

apps/server/src/core/ai-chat/tools/docmost-client.loader.ts

@@ -55,6 +55,11 @@ export interface DocmostClientLike {
   getOutline(pageId: string): Promise<Record<string, unknown>>;
   getPageJson(pageId: string): Promise<Record<string, unknown>>;
   getNode(pageId: string, nodeId: string): Promise<Record<string, unknown>>;
+  searchInPage(
+    pageId: string,
+    query: string,
+    opts?: { regex?: boolean; caseSensitive?: boolean; limit?: number },
+  ): Promise<Record<string, unknown>>;
   getTable(pageId: string, tableRef: string): Promise<Record<string, unknown>>;
   listComments(pageId: string): Promise<unknown[]>;
   getComment(