fix(ai): keep latest session request owner

[HandSonic]

Related issue

N/A - no matching issue was found.

Summary

Historical AI session loads had no latest-request ownership, so an older response or finally could overwrite a newer session and clear its loading state. An externally-triggered new chat also scheduled a send through a stale render closure, carrying the previous session/history. This change introduces a session generation coordinator, invalidates loads on new chat, and resolves external sends from their explicit new-session owner.

Affected surfaces

• Frontend / Web
• Backend / API / Storage
• Database plugin / Driver
• JCEF / Desktop packaging
• CI / Build / Release
• Documentation only

Verification

• Commands and results:
  • Session coordinator tests: passed for A/B reverse completion, stale finally, new-chat invalidation, and external send context.
  • Retired-AI contracts: passed.
  • Targeted ESLint: passed.
  • Full Community prebuild, Umi/Webpack build, and production bundle verifier: passed.
  • Fork code and CodeQL checks: passed.
  • Playwright: A/B reverse completion, stale finally loading ownership, and new-chat invalidation all passed with delayed mocked history responses.
  • Pairwise merge-tree with fix(ai): keep latest mention table request #2833: passed.
• Manual verification: Passed in the Community workspace AI panel with delayed A/B history responses.
• UI evidence: N/A

Risk and compatibility

• Public API or stored data: No public API or persisted history format changes.
• Database or driver compatibility: N/A.
• Network, privacy, or security: Prevents messages from being sent with an unintended prior session context.
• Community / Local / Pro boundary: Shared Community AI session UI.
• Backward compatibility: Current-session loads and ordinary sends retain existing request payloads.

Reviewer map

• Start here: sessionRequestCoordinator.ts, then AI.handleLoadSessionById, handleNewChat, and handleSend.
• Failure condition: stale loads commit messages/errors/loading, or an external new chat sends the old session/history.
• Rollback or disable path: Revert commit 862b39fb1b9f83d25ab84656edb27def42cff426; no migration is required.

Contributor declaration

• I linked the Issue that defines this change.
• I tested the affected behavior and reported the actual results above.
• I did not include credentials, private data, or generated build output.
• I disclosed substantial AI assistance below, or this PR contains no substantial AI-generated code.

AI assistance: OpenAI Codex assisted with diagnosis, implementation, automated tests, verification, and adversarial review.