fix(desktop): cancel stale session resume on new chat

[Astyyym]

Summary

• invalidate an in-flight session resume as soon as a new-chat draft starts
• prevent stale profile-lookup or gateway-swap continuations from reselecting the old session
• add a regression test for resume A -> New Chat -> stale resume completion

Testing

• git diff --check
• TypeScript check reaches the modified test without errors; remaining module-resolution errors are caused by running Windows Node against a WSL worktree
• Vitest cannot start in this environment because Vite's watcher treats a linked workspace module as a directory; please rely on Linux CI for the full suite

[teknium1]

Thanks for targeting the stale-resume generation race. The invalidation is the right mechanism, but it needs one more guard to cover the gateway-swap path described in the PR.

Problems

• At apps/desktop/src/app/session/hooks/use-session-actions/index.ts:224, the PR invalidates a resume when New Chat starts. However, resumeSession checks the token only before await ensureGatewayProfile(sessionProfile) (PR-head lines 507-511). A New Chat during that await can still reach the warm-cache write at lines 538-544 or the cold-path selection at lines 578-598 and revive the old session.

Suggested changes

• Re-check isCurrentResume() immediately after await ensureGatewayProfile(sessionProfile) and return before takeWarmCache() or any session-state writes.
• Add a deferred gateway-profile test alongside the profile-lookup case, with New Chat occurring while the gateway swap is pending.

Automated hermes-sweeper review.

[teknium1]

This invalidates the lookup phase, but resumeSession does not re-check the token after await ensureGatewayProfile(sessionProfile). A New Chat during that gateway-swap await can still enter the warm/cold paths and reselect the old session; add an isCurrentResume() guard immediately after that await and cover it with a deferred-swap test.

[Astyyym]

You're right: the prior invalidation covered only the profile lookup. I added isCurrentResume() immediately after await ensureGatewayProfile(sessionProfile), before either the warm or cold resume path. The new deferred-swap regression covers: resume A -> wait until its profile swap is pending -> New Chat -> resolve the swap -> assert A cannot issue session.resume or restore active, selected, or message state. The targeted use-session-actions suite now passes: 20/20 tests. Pushed in 93fea22.