fix(resolvers): question-log session_id becomes a substitution placeholder + stale-comment sweep

The question-log block bound $_SESSION_ID, a shell variable the
consolidated fence never sets — hook-less hosts logged empty session_id,
breaking /plan-tune per-session grouping. It now uses the same
substitute-from-the-skill-start-echoes contract as the telemetry block.
Also: retired the pre-Phase-2 stop-gate docstring, repointed the
gbrain-local-status cross-reference at the script's inline jq, dropped an
orphaned section comment, documented retro-metrics' suffix-only census.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

scripts/resolvers/preamble/generate-brain-sync-block.ts

@@ -6,9 +6,10 @@
  * daily pull, queue-depth status) now runs inside `bin/gstack-skill-start`
  * (invoked by the Preamble fence above) and reports through the same STATUS
  * lines it always emitted: the GBrain hint text and the `ARTIFACTS_SYNC:`
- * line. What remains here is the prose the model acts on — including the
- * one-time privacy stop-gate, which stays inline until the Phase 2
- * instruction-emission layer moves it behind its runtime gate.
+ * line. What remains here is the prose the model acts on. The one-time
+ * privacy stop-gate moved behind its runtime gate in Phase 2: it now arrives
+ * as a GSTACK_INSTRUCTION block from gstack-skill-start when consent is
+ * actually pending; this generator only carries the interpretation prose.
  *
  * Skill-END sync is no longer a separate fence: `bin/gstack-skill-end`
  * (invoked by the Telemetry step) drains the queue before logging.