fix(showcase): restore theming and verify UI 3.2 behavior

[pathscale]

The UI 3.2 showcase had retained its visual design while losing material behavior from the older theming page, omitting public component families, and leaving enabled controls without proven outcomes or stable semantic identities.

This branch restores the theme-library workflow with UI components: add, select, rename, delete, and clear saved themes; apply the current theme to the whole site; remember it across route teardown; restore it at startup; and preserve compatibility with older saved state that has no theme IDs.

The showcase imports UI's canonical family manifest and fails its build if any of the 101 public families has no dedicated page or coverage example. The complete-coverage route uses real consumer compositions for the remaining families, including FlexGrid, ComboBox, color controls, auth composition, install prompts, chat, and ImmersiveLanding. Fullscreen examples restore document layout both through their return action and through normal route navigation.

The control audit also:

• gives every discovered control a stable caller-owned ID and a named native outcome;
• derives repeated calendar days, saved-theme rows, theme tokens, radius choices, and other repeated controls from stable data keys;
• gives read-only and script-updated components the same public ID contract;
• gives every landing-page, header, Layouts, and theming-preview action a native outcome;
• exercises Slider and Color Picker through keyboard and viewport-bounded pointer input;
• restores exact Calendar, Navbar, Dropdown, theme persistence, theme export, and preview-action checks;
• uses UI controls throughout the showcase additions;
• contains no Cytoscape, canvas, or getContext implementation.

Local release evidence:

• typecheck and production build pass
• 600/600 native ps-qa outcomes across 13 groups
• complete coverage 87/87, including a read-only Progress addressed and updated by its authored ID
• theming 174/174
• navigation 45/45
• input 46/46
• all 101 public UI families are mapped with zero manifest gaps
• inventory discovers 287 controls: 287 outcome-attributed, zero unverified, zero missing IDs, zero unstable IDs, zero duplicate IDs, zero anonymous, and zero unreachable
• the run installs the published @pathscale/ui@3.2.1 npm tarball with SHA-256 7a468c51d3adfea2b5e2e4f711c92eaf775e600c2b1bd8bf05fab37a94bfcb1b; its built output is semantically identical to the reviewed candidate after normalizing the release version and JSON object ordering

The repository's documented bun run lint command is a no-op because it installs the unrelated biome@0.3.3; it is not claimed as release evidence here. A real Biome 1.5 read-only pass was used on the touched sources to catch the one explicit any in scope without introducing a repository-wide formatting change.

This PR does not merge or deploy the site. The owner reviews it first.