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>

bin/gstack-retro-metrics

@@ -297,6 +297,9 @@ echo "PRS_REFERENCED: $(printf '%s' "$_PRS" | wc -w | tr -d ' ')"
 [ -n "$_PRS" ] && echo "PR_REFS: $_PRS" || true
 
 # ── Test health (repo-wide + window) ─────────────────────────────────────────
+# Deliberately suffix-only (narrower than is_test's dir-based patterns): the
+# repo-wide census counts conventional test FILES; is_test additionally counts
+# dir-homed helpers toward test-insertion ratios.
 _TF_TOTAL=$(git ls-files 2>/dev/null | grep -cE '(\.test\.|\.spec\.|_test\.|_spec\.)' || true)
 case "$_TF_TOTAL" in ''|*[!0-9]*) _TF_TOTAL=0 ;; esac
 echo "TEST_FILES_TOTAL: $_TF_TOTAL"