Improve AdaptiveTabBar layout when content does not fit

[kean]

Fixes CMM-1159: Fix an issue with AdaptiveTabBar .fill distribution.

Changes

Refactors AdaptiveTabBar to automatically select the optimal layout based on available width.

1. Fill Equally – when all buttons with equal width fit the screen
2. Fill Proportionally (Full Width) – when all buttons with proportional widths fit the screen
3. Fill Proportionally (Scrollable) - when buttons can't fit

Additionally:

• Custom TabButton control replaces UIButton to prevent layout jumping when selection changes font weight
• Improved accessibility with proper button traits and selected state

Screenshots

Before / After

Stats:

Interactions:

Screen.Recording.2026-01-19.at.5.23.58.PM.mov

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

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📲 You can test the changes from this Pull Request in WordPress by scanning the QR code below to install the corresponding build.

	App Name	WordPress
	Configuration	Release-Alpha
	Build Number	30486
	Version	PR #25146
	Bundle ID	org.wordpress.alpha
	Commit	08a5b43
	Installation URL	01331rqc3331o

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📲 You can test the changes from this Pull Request in Jetpack by scanning the QR code below to install the corresponding build.

	App Name	Jetpack
	Configuration	Release-Alpha
	Build Number	30486
	Version	PR #25146
	Bundle ID	com.jetpack.alpha
	Commit	08a5b43
	Installation URL	4t0i9j8409a0g

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