Swap tab groups to render icon only to match tabs

[johnturcoo]

Description

When tabs shrink to a certain size in the horizontal tab bar, they stop displaying the tab name and just show their icon. This PR modifies tab group headers to follow the same behavior.

How it works

• Wrapped the group header in a SizeConstraintSwitch that swaps the full layout (collage + name) for a compact, icon-only collage below COMPACT_TAB_WIDTH_THRESHOLD (42px) — the same mechanism and threshold TabComponent already uses, so headers and tabs go compact at the same width.
• The compact collage renders at the tab's compact icon size (TAB_INDICATOR_HEIGHT, 14px), centered

Linked Issue

https://linear.app/warpdotdev/issue/APP-4777/tab-group-header-icon-collage-is-clipped-when-many-tabs-open

Testing

• I have manually tested my changes locally with ./script/run

Screenshots / Videos

Demo before

Demo after

[oz-for-oss]

@johnturcoo

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Overview

This PR makes horizontal tab group headers switch from the full collage-and-title layout to an icon-only collage at the same width threshold used by tabs. The attached before/after Loom links satisfy the repo's visual-evidence requirement, and I did not find security findings or spec-drift concerns because no approved spec context was provided.

Concerns

• The new responsive header is still laid out as a non-flex child of the group row, so it receives an unbounded horizontal constraint and the SizeConstraintSwitch cannot observe the finite tab slot width it is meant to compare against.

Verdict

Found: 0 critical, 1 important, 0 suggestions

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[oz-for-oss]

⚠️ [IMPORTANT] This header is added to render_horizontal_tab_group as a normal Flex child, and Flex lays non-flex children out with an unbounded main-axis constraint. With constraint.max.x() infinite, WidthLessThan(COMPACT_TAB_WIDTH_THRESHOLD) never matches; the default full row also uses MainAxisSize::Max, which tries to expand to infinity. Make the header a finite flex slot (for example by wrapping it in Shrinkable::new(1.0, ...) at the group-row call site) before switching on width.