fix(web): back-to-back messages stack tight with joined corners - #27978

Eligibility
Adjacent messages gain joined corners and tighter spacing, with existing actions placed beside grouped bubbles where space permits. The changes are limited to presentation, retaining below-message actions for narrow and touch layouts.

Additional Thinking

Your Custom Policy

Default criteria apply. This is a presentation adjustment, not a change to product defaults or default settings, and the assessed diff adds no static-analysis suppression directives; neither mandatory-human-review condition is triggered.

Code

Adds previous-message grouping metadata and updates row reuse checks. Tightens adjacent message/media corners and moves grouped-message actions beside bubbles on wide, fine-pointer layouts; narrow and touch layouts retain actions below. Existing action handlers and payloads remain unchanged. The ignored file was not reconstructed.

Review Context

Author has write access; no ownership requirements were supplied. Two threads are resolved and no unresolved comments were supplied. The author reports dev-app verification. Retrieved checks show successful lint, build/typecheck and correctness checks, with web tests still running; CI state did not determine the recommendation. No blocking severity configuration was supplied.

Verdict

The understood changes are confined to timeline presentation and responsive placement of existing controls. They do not change persistent data, external operations, permissions or action semantics, and carry no obvious material risk requiring human judgment.

Notes:
No code owners found in target merge base 80a2351

Agent Credits: 30 credits
Approvability runs at a flat rate of 30 credits whenever the agent is asked for a verdict.