feat: [ENG-2858] wire runtime-signal sidecar in tool-mode curate write and query read paths

Adds bumpSidecarOnCurateWrite / bumpSidecarOnQueryRead helpers and wires them
into the four touchpoints that previously left sidecar signals stale: the
daemon's curate-html-direct task, the CLI curate-session writer, the
SearchExecutor, and the QueryExecutor's executeToolMode return. Prereq for
prune candidate generation which ranks topics by importance, recency, and
accessCount.