chore: hygiene pass — ruff clean, docs storage-model truth, replay /me, failSession log

Audit findings 6.1-6.4 + the audit's remediation plan itself
(docs/superpowers/plans/2026-07-20-full-audit-remediation-plan.md).

- ruff: 34 → 0 (unused imports/f-strings auto-fixed; E702 semicolon lines
  split in test files; one unused local dropped). Suite still 819 green.
- CLAUDE.md + PROJECT_STATE.md no longer claim "no database / settings in
  settings.json": the harness selects filesystem OR PostgreSQL session
  storage (repository.py, server mode), and settings flow through harness
  preferences with the JSON file as fallback only.
- tools/replay: stub /me (SPA boot was parsing the SPA's own HTML as JSON)
  and /runtime/prewarm.
- failSession best-effort persistence now logs its failure server-side
  instead of vanishing.

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

harness/tests/test_decisions_retract.py

@@ -8,7 +8,7 @@ def test_decision_retracted_in_audit_but_marked(tmp_path):
     d1 = append_decision(
         session, type="table_promoted", subject="phase:4", detail="t1", rationale="r"
     )
-    d2 = append_decision(
+    append_decision(
         session,
         type="decision_retracted",
         subject="phase:4",