Add search_raw() over the raw/ ingest directory for verbatim recall
when compiled concepts miss. New op kb_search_raw is exposed through
CLI / HTTP / MCP via the operations registry. source_url is only
emitted for http(s) URLs (local paths scrubbed); top_k is clamped
to a non-negative range; absolute filesystem paths are not returned.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>