fix(tab-button): apply correct focused background color in dark palette

[gnbm]

Issue number: resolves resolves internal

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What is the current behavior?

In the dark palette, focused ion-tab-button elements do not receive the ion-focused class, so the focus indicator is never shown.
The --ion-tab-bar-background-focused token was also not set, causing the focused state to fall back to get-color-shade(#fff) (#e0e0e0) — a light grey that is invisible on a dark background.

What is the new behavior?

• --ion-tab-bar-background-focused is defined in the dark palette: #0b0b0b for iOS and #1b1b1b for MD, providing a subtle dark-appropriate focus indicator.
• A new e2e test verifies that the focused ion-tab-button receives the ion-focused class and does not render with the light-mode fallback color in the dark palette.

Does this introduce a breaking change?

• Yes
• No

Other information

The test triggers keyboard mode (required by focus-visible.ts) before focusing the inner <a> element inside the tab button's shadow DOM, since calling .focus() on the host element is a no-op without delegatesFocus.

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Project	Deployment	Actions	Updated (UTC)
ionic-framework	Ready	Preview, Comment	Mar 30, 2026 10:10pm