feat(themes): add built-in High Contrast Dark and Light themes

[SagarSDagdu]

Description

Adds two accessibility-focused built-in themes selectable from the theme chooser:

• High Contrast Dark — black background, white foreground, yellow accent
• High Contrast Light — white background, black foreground, deep-blue accent

ANSI palettes use fully saturated colors targeting WCAG AAA contrast against the background. The dark theme's blue is lifted from pure #0000FF to #4080FF because pure blue's luminance is too low to read on black.

The change follows the same pattern as the other 23 bundled themes: color constants and WarpTheme constructors in default_themes.rs, new ThemeKind variants wired through Display and WarpThemeConfig::new() in theme.rs.

Linked Issue

Fixes #11043.

• The linked issue is labeled ready-to-spec or ready-to-implement.

Screenshots / Videos

Testing

• cargo check -p warp passes
• Manually verified both themes render in the theme chooser and apply correctly to the terminal (built-in palette + UI chrome)

Agent Mode

• Warp Agent Mode - This PR was created via Warp's AI Agent Mode

[oz-for-oss]

@SagarSDagdu

This PR is not linked to an issue that is marked with ready-to-implement.

Issue-state enforcement details:

• Associated same-repo issues checked: Add high contrast theme #11043

• Required readiness label: ready-to-implement

Readiness check:

• Add high contrast theme #11043: missing ready-to-implement; readiness labels present: none

To continue, link this PR to a same-repo issue such as Closes #123 in the PR description, and make sure that issue has ready-to-implement.

Powered by Oz

[oz-for-oss]

@SagarSDagdu

This PR is not linked to an issue that is marked with ready-to-implement.

Issue-state enforcement details:

• Associated same-repo issues checked: #11043

• Required readiness label: ready-to-implement

Readiness check:

• #11043: missing ready-to-implement; readiness labels present: none

To continue, link this PR to a same-repo issue such as Closes #123 in the PR description, and make sure that issue has ready-to-implement.

Powered by Oz