fix: keep code-block toolbar within panel bounds when sidebar is narrowed

[bunnysayzz]

Description

Fixes #13085 — when the Continue sidebar/panel is narrowed, the code-block header bar (Copy/Run/Enter buttons) does not resize and the action buttons get hidden under the sidebar edge. Explanation text between code blocks could also overflow.

Root cause: the toolbar header is a flex row whose children have flexbox's default min-width: auto, which prevents them from shrinking. The root container has overflow-x: hidden, so when the panel narrows, the button row is pushed past the visible area and clipped.

Fix (in StepContainerPreToolbar):

• Title side (filepath/language + chevron): added min-w-0 so it can shrink; the filepath already truncates via line-clamp-1 break-all.
• Action-button side: added shrink-0 so Copy/Run/Apply buttons are never clipped.
• Header row: added flex-wrap + gap-x-3 gap-y-1 so on very narrow widths the buttons wrap to a second line instead of overflowing.

This targets the code-block header specifically (the issue's primary symptom). Explanation-text reflow stems from the same overflow root and is also relieved once the block no longer forces itself wider than the panel.

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Checklist

• I've read the contributing guide
• The relevant docs, if any, have been updated or created
• The relevant tests, if any, have been updated or created

Screen recording or screenshot

When the sidebar is narrower than the code-block toolbar, the buttons now stay visible (title truncates / buttons wrap) instead of being clipped at the panel edge.

Tests

Added gui/src/components/StyledMarkdownPreview/StepContainerPreToolbar/index.test.tsx:

• smoke test (component renders)
• regression test asserting the title container has min-w-0 (shrinkable) and the action-button container has shrink-0 (never clipped)

All 44 tests in StyledMarkdownPreview/ pass (npx vitest run src/components/StyledMarkdownPreview/). tsc --noEmit shows only pre-existing workspace-package resolution errors in core/ (unbuilt @continuedev/config-yaml), none in the changed files.

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[bunnysayzz]

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