[Bl0ck154]

Fixes the v0.2.12 OAuth regression reported in #136.

The main issue is that background usage/metadata refreshes can refresh OAuth solely because the stored ID token is expired, even while the access token and live Codex session are still valid. With rotated/single-use refresh tokens this can surface refresh_token_invalidated / refresh_token_reused and incorrectly make valid accounts look logged out.

Changes:

• background usage, warm-up and metadata refresh only refresh OAuth when the access token is actually expired/near expiry;
• account switching still prefers a full token refresh, but falls back to an existing usable access token if refresh fails, instead of aborting the switch;
• known refresh-token failures are mapped to human-readable messages instead of dumping raw backend JSON into the account card;
• when Codex is running, Switch now opens the existing force-close-and-switch flow instead of behaving like a dead/disabled action; the button label remains simply Switch.

Validation:

• frontend production build passes (tsc && vite build);
• Rust test suite passes: 49 passed, 0 failed.

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Maintenance triage — 2026-09-30

Continue in: #185.

OAuth refresh policy is consolidated in #136 / #185, with the #182 cross-process persistence foundation. The force-close switch entry point is already present in main. The human-readable authentication-error presentation from this PR remains an acceptance concern in #136 and must be retained or split into an explicit follow-up before treating that issue as fully resolved. #185 is open and unmerged.