v0.51.9 — 2-PR batch (boot path + Codex session repair)

🐛 Fixed

#1735 by @dso2ng — Keep saved running sessions sidebar-only on root boot (slice of #1694). Fresh root / tabs no longer auto-project a still-running localStorage-saved session into the active pane; running sessions stay sidebar-only until the user opens them. Explicit /session/<sid> URL behavior unchanged.
#1738 by @Michaelyklam — Repair stale OpenAI session models for Codex. Closes #1734. Legacy sessions with model=openai/gpt-... and no model_provider were misrouted through OpenRouter under Codex. New repair path in _resolve_compatible_session_model_state() swaps to active Codex default + persists model_provider="openai-codex".

Opus follow-up: persist openai-codex provider unconditionally on the stale-session repair path so the resolved shape is stable across resolutions.

4584 → 4590 passing (+6 regression tests). 0 regressions. Full suite ~138s.

Both PRs CI-green individually + rebased onto current origin/master.
All JS files syntax-clean (node -c).
Browser API sanity (11/11 endpoints) — all pass.
Opus advisor: SHIP, 5/5 verification questions clean, 0 MUST-FIX, 1 SHOULD-FIX absorbed.
Pre-stamp re-fetch: both PR heads still match local rebases.

Slice of #1694 (boot path projection).

Full Changelog: v0.51.8...v0.51.9