Summary

• Prevent question dock programmatic focus from scrolling the session timeline away from the latest turn.
• Add a deterministic submit-to-question-dock E2E guard that keeps the timeline near bottom.
• Extend renderer diagnostics so the [Bug] Session jumps to top after submit enters question dock #467 scroll-jump shape is reported even when browser focus marks the sample as user-scrolled.

Why

Long sessions could jump from the latest turn to near the top after the user submitted a message and the assistant entered a pending question tool state. The user then lost the question dock position and had to manually scroll back down to answer.

Root cause boundary: this is a frontend session scroll/focus contract issue. The fix stays in the question dock focus behavior, session renderer diagnostics, and focused regression coverage. It does not touch backend question tools, blocker ledger, SSE replay, persistence, or protocol/schema layers.

Related Issue

Closes #467

Human Review Status

Pending. A human should make the final merge decision after reviewing the final diff and verification evidence.

Review Focus

• Confirm the question dock focus change uses preventScroll without breaking keyboard focus or option navigation.
• Confirm diagnostics only broadens detection for recent-submit + previous-near-bottom + near-top samples, not ordinary user-initiated scrolling.
• Confirm the E2E covers the real visible submit path for the final prompt instead of seeding the question dock directly.

Risk Notes

Low frontend risk. preventScroll changes only programmatic focus inside SessionQuestionDock; keyboard focus is still assigned and covered by the existing keyboard E2E. Diagnostics detection remains gated by recent submit and previous near-bottom state to avoid broad false positives.

How To Verify

Focused unit tests: 914 passed
Command: bun --cwd packages/app test:unit src/pages/session/use-session-scroll-dock.test.ts src/pages/session/composer/session-question-dock.test.ts src/context/renderer-diagnostics.test.ts

Focused E2E: 2 passed
Command: bun --cwd packages/app test:e2e --grep "submit to question dock keeps latest turn visible|blocked question flow supports keyboard shortcuts"

Typecheck: passed
Command: bun --cwd packages/app typecheck

Diff check: passed
Command: git diff --check

Screenshots or Recordings

Not included. This bug is hard to reproduce manually in the desktop shell, so the behavior is locked with a deterministic Playwright path: long visible history, real visible prompt submit, pending question dock, timeline remains near bottom. Existing and new E2E also verify keyboard focus still works.

Checklist

• Human review status is stated above as pending, approved, or not required
• I linked the related issue, or stated why there is no issue
• This PR has type, primary area, and priority labels, or I requested maintainer labeling
• I described the review focus and any meaningful risks
• I listed the relevant verification steps and the key result for each
• I did not introduce unrelated refactors, dependencies, generated files, or file changes beyond the stated scope
• I manually checked visible UI or copy changes when needed, with screenshots or recordings
• I considered macOS and Windows impact for platform, packaging, updater, signing, paths, shell, or permissions changes
• I called out docs, release notes, dependencies, permissions, credentials, deletion behavior, generated content, or local file changes when relevant
• I reviewed the final diff for unrelated changes and suspicious dependency changes
• I am targeting dev, and my PR title and commit messages use Conventional Commits in English