fix(gui): prevent Accept/Reject buttons from being clipped in narrow sidebar

[thanhnnict]

Summary

The PendingToolCallToolbar buttons (Accept/Reject) are clipped when the sidebar panel is narrow or after extended chat sessions with many code blocks/terminal outputs.

Root Causes

1. Toolbar used flexbox with shrink-0 on buttons container, causing overflow when panel width was insufficient
2. Pre elements used max-width: calc(100vw - 24px) which could expand content beyond the sidebar container width, pushing the entire layout outside the overflow-x: hidden boundary

Fix

• Switch toolbar row from flexbox to CSS Grid (grid-cols-[minmax(0,1fr)_auto]) ensuring buttons always receive their intrinsic width
• Replace viewport-relative max-width with container-relative (100%) for pre elements in both StyledMarkdownPreview and UnifiedTerminal
• Add overflow-x: hidden on StepsDiv to contain chat content
• Add min-w-0 on flex containers to allow proper shrinking

Testing

• Tested with narrow sidebar (~300px) — buttons always visible
• Extended chat sessions with multiple terminal outputs — no overflow
• Code blocks render with horizontal scroll inside their container (no layout push)

Changed Files

File	Change
PendingToolCallToolbar.tsx	flex → grid layout
Lump/index.tsx	Add min-w-0, overflow-hidden
StyledMarkdownPreview/index.tsx	calc(100vw-24px) → 100%
UnifiedTerminal.tsx	calc(100vw-24px) → 100%
Chat.tsx	StepsDiv overflow-x: hidden
gui/index.tsx	Main min-w-0

[thanhnnict]

Hi maintainers,

The only failing check is jetbrains-tests which appears unrelated to this change — this PR only modifies GUI components (CSS layout in PendingToolCallToolbar, StyledMarkdownPreview, UnifiedTerminal, Chat.tsx, and Lump).

All other 46 checks pass, including gui-checks, core-checks, prettier-check, lint, all e2e tests, and all platform builds.

Could you re-run the JetBrains tests or confirm if this is a known flaky test? Thanks!