Restore routing and the UI showcase interactions

[pathscale]

The UI showcase had several production-visible regressions: Chrome route transitions could tear down the Solid effect incorrectly, global search reloaded or remained over the next page, the theme builder had drifted from AgencyZero's composition controls, glass and depth controls did not reliably affect the preview, and the site still consumed UI 3.2.1.

This restores one persistent router-owned layout, adds in-place desktop/mobile search over every registered route, rebuilds the theme composer with the full colour flower and separate control/art accents, delegates glass curves to @pathscale/ui 3.2.2, restores random/reset/persistence/export behavior, and makes the showcase responsive. CSS export now escapes arbitrary theme names and only reports copy success after the clipboard write resolves. The production policy gate rejects Google Fonts and CSP policies that block UI's dynamic styles.

Validation performed locally before push:

• ps-qa 0.7.2 + rebuilt chuzz-headless: 669/669 checks across all 13 groups
• post-review theming rerun: 235/235, including real pointer sliders and terminal clipboard success
• rendered inventory/reconciliation: 354/354 controls have named outcomes; 0 anonymous, missing, unstable, duplicate, manual, or unverified controls
• Chrome 152 desktop: in-place navigation retains the layout, search closes/reopens correctly, every theme/glass slider changes through real mouse input, random/reset/persistence/export pass, and no runtime errors occur
• Chrome 152 mobile: editor/preview switching, search focus, metacharacter queries, navigation, drawer dismissal, duplicate IDs, runtime errors, and failed URLs all pass
• hostile CSS export name (Ocean "Night" \\ reef): exported selector parses and matches the exact name; clipboard bytes exactly match the generated CSS
• bun run build and bun run typecheck
• bun run qa:production-policy

No deployment or merge is included.