fix(web): collapse expanded composer immediately on submit

[techotaku39]

Summary

• Collapse the expanded composer as soon as a send is dispatched.
• Remove the settlement plumbing that made the layout wait for mutation success.
• Preserve queued delivery, optimistic messages, and send-error/attachment recovery behavior.
• Add regression coverage for immediate collapse and delayed failures.

Problem / Motivation

The full-screen composer stayed expanded until the message POST completed successfully. When the network was slow or a message waited behind a running Agent turn, the user could see the send action happen while the full-screen editor remained open.

The composer is a transient editing surface, so its layout should respond immediately to the submit action. Message delivery can continue asynchronously after the editor collapses.

Implementation

• Call setIsExpanded(false) immediately before composer.send().
• Remove the obsolete sendAcceptance / sendSettlement presentation path.
• Keep queued delivery and failed-send recovery behavior unchanged.
• Update focused composer and send-hook tests.

Validation

• bun typecheck — passed.
• bun run --cwd web test src/components/AssistantChat/HappyComposer.sendError.test.tsx src/components/AssistantChat/HappyComposer.expandSelection.test.tsx src/hooks/mutations/useSendMessage.test.tsx — 57 tests passed.
• bun run build — passed.
• Isolated Full Live Playwright verification — 2 tests passed:
  • delayed real message POST response: the composer collapsed before the response was released;
  • real Claude Runner queue: the second queued message collapsed immediately and was executed once.

Scope and Risk

• Web-only behavior change.
• No API schema, database migration, dependency, or Runner behavior changes.
• Failed sends now leave the composer collapsed while preserving the existing draft and error recovery flow.

Related Issues

Refs #1368

Refs #1580

AI Disclosure

Implementation, tests, and PR preparation were assisted by OpenAI Codex (GPT-5.6).

[github-actions]

Findings

• None.

Summary
Review mode: initial
No Blocker, Major, Minor, or Nit findings in the added or modified lines. Residual risk: the focused composer tests mock assistant-ui’s synchronous send path; the full test check was still pending at review time.

Testing

• Not run (automation). GitHub integration passed; test pending.

HAPI Bot