fix(web): fix subagent row left border being cut off

[sameerr03]

What Changed

The subagent spawn summary no longer shifts outside the clipped chat timeline. Removing its redundant negative horizontal margin keeps the rounded left border visible while preserving the full-width row.

Why

The surrounding work-group layout already balances its negative margin with matching padding. The nested -mx-1 moved the subagent row four pixels past the timeline boundary, where horizontal overflow clipping hid its left edge.

UI Changes

Before	After

Validation

• vp fmt --check apps/web/src/components/chat/MessagesTimeline.tsx
• vp lint apps/web/src/components/chat/MessagesTimeline.tsx
• vp test run apps/web/src/components/chat/MessagesTimeline.test.tsx (20 tests)
• git diff --check
• Reproduced before the change and verified after hot reload in a real vp run dev thread

Checklist

• This PR is small and focused
• I explained what changed and why
• I included before/after screenshots for the UI change
• A video is not applicable because this is a static layout fix

Implemented with GPT-5.6-sol in the Codex harness.

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Note

Low Risk
Single Tailwind class change on a chat UI row; no logic, API, or data impact.

Overview
Fixes a chat timeline layout bug where the subagent spawn summary row’s left rounded border was clipped.

The AgentSpawnCtaRow button no longer uses -mx-1. That extra negative horizontal margin stacked with the parent work-group’s -mx-1 / px-1 and pushed the row past the timeline’s overflow-x-clip boundary, hiding the left edge. The row still spans full width inside the group with the rest of its styling unchanged.

^{Reviewed by Cursor Bugbot for commit a75d43d. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Fix AgentSpawnCtaRow border visibility by removing negative horizontal margin

Removes the -mx-1 Tailwind class from the CTA button in MessagesTimeline.tsx, restoring the subagent row border visibility that was being clipped by the negative margin.

^{Macroscope summarized a75d43d.}

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[macroscopeapp]

Approvability

Verdict: Approved a75d43d

Single-line CSS change removing a negative margin class to fix border visibility. Pure styling fix with no runtime behavior impact.

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