Add shared and TDA component gallery

[jmchilton]

What

• add a /gallery/ page that renders every current @galaxy-foundry/site-kit/specimens group with this foundry's styling
• add five TDA-specific specimen groups covering reference kinds and the local filtration, persistence, point-cloud, and topology flourishes
• generate standalone routes for shared specimens that require isolated or document rendering
• link the gallery from the design records page and centralize theme imports for standalone pages
• record the shared-versus-local gallery boundary in the checked code-architecture design record
• adopt the released @galaxy-foundry/site-kit 0.9.2 contract
• assert complete specimen coverage, iframe routes, inbound navigation, and search policy in the built-site tests

Why

This gives the foundry a living visual acceptance surface without forking upstream gallery machinery. Shared examples come directly from the site-kit specimen contract, while TDA-specific visual language remains owned and styled locally.

The companion upstream work is merged and released, so this branch now consumes the polished
contract and follows the accepted adoption instructions:

• Keep gallery proof aligned with site-kit specimens foundry-lib#99
• Document component gallery acceptance galaxyproject/foundry-pattern#54

Impact

The public site gains the gallery and nine standalone specimen routes. Existing component behavior and content routes remain unchanged.

Checks

• pnpm validate
• 119 tests passing
• Astro typecheck with 0 diagnostics
• production build emitting 112 pages