[Open-Squilla]

Completed chat activity could leave hundreds of blank pixels below the final answer because absolutely positioned screen-reader text escaped the collapsed clipping element. Make that element the positioning container so its existing clip also bounds those descendants.

Scope

Scope boundary: One CSS positioning rule, a synthetic browser regression, and registration in the CI browser inventory with both inventory assertions updated. Existing browser shard assignments stay unchanged.
Non-goals: Backend runtime and virtual-list algorithms.

Branch

Base branch: main
Target exception: N/A

Issue

Linked issue: None
If None, reason: Standalone UI regression with no associated public issue.

Release Note

Release note: Fix excess blank space below completed chat responses when activity is collapsed.

Tests

Ruff: Passed for src, tests, and the browser suite selector.
Pytest: 262 passed in the browser-inventory and workflow contract files with Bash 5.3; 31-case preflight passed first.
Build: npm run build passed architecture checks, TypeScript checks, artifact verification, and staging. uv build --wheel passed.
Regression tests: added

• 316 related WebUI unit tests passed.
• 59 Chromium browser tests passed against the built artifact, with retries disabled.
• Four new regression cases cover 900px/1600px layouts, normal/reduced motion, keyboard expansion/collapse, reload, and switching tasks.
• The new regression failed against the original CSS with 683px of extra scrollable overflow, then passed with the fix.
• The new file is included in general-4; CI inventory checks retain exact membership and one-time assignment.

Notes: Platform-neutral CSS. Browser validation ran on macOS/Chromium; native Windows/Linux clients were not run locally. Full backend coverage is left to GitHub CI. All browser fixtures are synthetic, offline, and credential-free. Independent read-only review completed; the follow-up inventory assertion finding was addressed and rechecked.

Maintainer Live Check

Maintainer live check: no
Surface: N/A

Safety

Only source and synthetic regression tests are included. No secrets, private transcripts, session artifacts, generated bundles, or machine-specific paths are committed.

Third-Party Origin

Third-party origin: none

[github-actions]

Merge queue CI: failure — run 40369256954, attempt 1.
Tested queue candidate: cffa2fb5cf02af90a1fb9976253d0dadf2ee498d. This result belongs to that combined tree, not necessarily the PR's current head.

• Windows high-risk (recovery-migration-1): failure
• CI result: failure

The run summary lists reused suites and executed checks. A green PR check alone does not mean queue validation has passed.

[github-actions]

Merge queue CI: failure — run 40373290093, attempt 1.
Tested queue candidate: 55fdd50dccfc257f63d88f333a7b609b3de24b85. This result belongs to that combined tree, not necessarily the PR's current head.

• Windows high-risk (gateway-sqlite-3): failure
• Desktop recovery E2E (windows-latest, profiles-profile-import-flow): failure
• Desktop recovery E2E (windows-latest, profiles): failure
• Windows NSIS acceptance / upgrade-and-start (0.5.4, default, baseline): failure
• Windows NSIS acceptance / upgrade-and-start (0.5.4, default, longpath): failure
• Windows profiles exact-once coverage: failure
• Windows NSIS acceptance / Windows NSIS acceptance result: failure
• CI result: failure

The run summary lists reused suites and executed checks. A green PR check alone does not mean queue validation has passed.

[github-actions]

Merge queue CI: success — run 40376609777, attempt 1.
Tested queue candidate: 1cda21446d5d48a77f1af3a4249e943b9ebe9654. This result belongs to that combined tree, not necessarily the PR's current head.

The run summary lists reused suites and executed checks. A green PR check alone does not mean queue validation has passed.