🦔 fix: Keep System Messages Stable During Collapse

[lia-by-librechat]

Summary

Collapsing a system background-task message briefly stretched its bubble to the full available width before returning to its compact header. Keep the expanded width while the result body animates closed, then restore the compact width when that body unmounts. Subagent wake-up cards use the same sizing rule.

How it works

-isExpanded && 'w-[36rem]'
+shouldRenderBody && 'w-[36rem]'

Width and result-body lifetime now change together instead of releasing width at the start of the closing transition.

Type of change

• Bug fix

Testing

• Focused client tests: 41 passed across wake-up cards, message rows, and shared transcripts.
• Client tsc --noEmit: passed.
• Regression coverage checks closing width, lazy unmount, inert content, nested transition events, and reopening before collapse completes.
• npm run static-checks -- --against origin/dev: passed.
• Real shared-transcript UI in Chromium: desktop, mobile, reduced motion, lazy unmount, and interrupted reopening passed.
• Local runtime: Node 24.16.0 for npm/Jest/TypeScript; Bun 1.4.2 for the browser driver.
• Full end-to-end suite and Lighthouse were not run locally. CI Lighthouse passed.
• Independent source review of ce3dd9f13a9e7a5b46b305ddfc8160342c2311fb: complete, no findings.

Screenshots / recordings

Before/after recordings were captured from the running app at the same desktop viewport. Uploading with gh --attach returned unsupported authentication type, so the recordings could not be attached.

Collapse width	Before	After
Expanded	602 px	602 px
Peak while closing	639.1875 px	602 px
Collapsed	298 px	298 px

Risk / compatibility

No API, preference, theme, or animation-duration changes.

Checklist

• I reviewed my own changes
• Relevant tests have been added or updated
• Existing relevant tests pass
• The change does not introduce new warnings or errors
• Required dependency changes have been merged/published: N/A
• Required documentation PR: N/A

[lia-by-librechat]

Head: ce3dd9f. Keeps wake-up card width until the closing result body unmounts. Adds collapse and interrupted-reopen regressions for background-tool and subagent cards. Focused client tests: 41 passed. Client typecheck passed.