fix(search): whitelist #529 search response-fields in the #494 prose drift-guard

The rebase pulled develop's #494 REVERSE prose drift-guard, which flags every
camelCase token in ROUTING_PROSE that is not a registered MCP tool. #529's search
routing prose documents the search RESPONSE fields matchedTerms/matchedFields/
hasMore/truncatedAtCap — genuine non-tool terms — so add them to
PROSE_NON_TOOL_TERMS (develop's designed allowlist). Reconciles both invariants:
#529's search-prose enforcement and #494's dead-reference guard both stay green.

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

packages/mcp/src/server-instructions.ts

@@ -72,6 +72,12 @@ export const PROSE_NON_TOOL_TERMS: ReadonlySet<string> = new Set([
   "parentCommentId",
   "suggestedText",
   "historyId",
+  // search RESPONSE fields documented in the routing prose (#529) — schema
+  // fields the search tool returns, not tools themselves
+  "matchedTerms",
+  "matchedFields",
+  "hasMore",
+  "truncatedAtCap",
   // helper / value fragments
   "orderedList", // "orderedList.type" (a dropped attr, not a tool)
   "mxGraph", // "mxGraph XML"