fix(chat): prevent overlap while virtual rows grow live

[khaliqgant]

Summary

• synchronously resize only the mounted chat row whose layout-affecting message props changed
• retain ResizeObserver measurement for initial size, viewport, font, and width changes
• add geometry regressions for an initially large agent_relay.post_message result and a live-growing result

Root cause

The tool-call payload renderer is ordinary block-flow markup, so overflow-visible and the fixed estimate are not the source of the persistent overlap. Initial large rows are measured correctly. The failure occurs when an already-mounted message grows: until the asynchronous ResizeObserver delivery updates the cached row size, the next absolute row keeps its old translateY and can paint over the newly taller content. The changed row now reports its committed offsetHeight to react-virtual from a layout effect, moving successor rows before paint.

Evidence

Before the fix, the live-growth regression rendered the first row at 788px while the second row remained at translateY(88px). The initial-large-payload case already passed, which ruled out content escaping normal flow. Both cases pass after the targeted synchronous resize.

Test plan

• npx vitest run src/renderer/src/components/chat/ChatView.dom.test.ts
• npm run test:all (129 Node tests and 607 Vitest tests)
• npm run typecheck
• npm run lint

Closes #424

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Review details

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: bcdcd572-4c63-4478-ba08-3f061462c9fd

📥 Commits

Reviewing files that changed from the base of the PR and between b52004a and f81c01f.

📒 Files selected for processing (2)

• src/renderer/src/components/chat/ChatView.dom.test.ts
• src/renderer/src/components/chat/ChatView.tsx

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/codex-424-chatview-overlap

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