chore(release): stamp v0.51.9 — 2-PR batch (boot path + Codex session repair) + Opus follow-up

Constituent PRs:
- #1735 (@dso2ng) — keep saved running sessions sidebar-only on root boot (slice of #1694)
- #1738 (@Michaelyklam) — repair stale OpenAI session models for Codex (closes #1734)

Plus 1 in-stage absorbed fix:
- Opus SHOULD-FIX: persist openai-codex provider unconditionally on stale-session
  repair (drop conditional catalog-coverage check that produced redundant
  repair-writes per chat-start).

Tests: 4584 → 4590 passing (+6). 0 regressions. Stably green.

Pre-release verification:
- Both PRs CI-green individually + rebased onto master
- pytest 4590 passed, 0 failed
- node -c clean on static/boot.js
- 11/11 browser API endpoints PASS
- Opus advisor: SHIP, 5/5 verification clean, 0 MUST-FIX, 1 SHOULD-FIX absorbed

Closes #1734.

ROADMAP.md

@@ -2,7 +2,7 @@
 
 > Web companion to the Hermes Agent CLI. Same workflows, browser-native.
 >
-> Last updated: v0.51.8 (May 6, 2026) — 4584 tests collected — 7-PR full-sweep batch (#1725-1730, #1732)
+> Last updated: v0.51.9 (May 6, 2026) — 4590 tests collected — 2-PR full-sweep batch (#1735, #1738)
 > Test source: `pytest tests/ --collect-only -q`
 > Per-version detail: see [CHANGELOG.md](./CHANGELOG.md)