fix(catalog): sync tab labels with the sliding indicator

[AksharP5]

What

The Tabs Slide Indicator starts with the pill under "Plan," but marks "Debug" as active. This keeps the active label aligned with the indicator before, during, and after the slide.

Fixes #3266.

Why

The component permanently styled the second button white even though the indicator starts under the first button. Its inactive gray also measured 4.4:1 against the track, just below WCAG AA.

How

The first label now owns the initial active state, and both label colors animate with the indicator. The inactive gray moves from #71717a to the nearest compliant shade, #6f6f78. The demo no longer pads its timeline with a no-op, and the generated Catalog payload is refreshed.

Test plan

• Unit tests added/updated
• Manual testing performed
• Documentation updated (generated Catalog payload)

Validated with:

• bun run build
• bun run lint:registry-items tabs-slide-indicator
• bunx oxfmt --check on all changed files
• npx hyperframes check --snapshots --samples 15 --at-transitions against the standalone demo
• Rendered and inspected the initial, moving, and settled states

The full HyperFrames gate reports zero lint, runtime, layout, motion, or contrast findings. All 12 sampled text states pass WCAG AA.

Before and after

comparison.mp4