fix(ui): trap drawer keyboard focus

[wyf027]

Summary

• keep Tab and Shift+Tab focus navigation inside an open Drawer
• add Drawer keyboard focus trap coverage with user-event tab navigation
• document Drawer focus looping and update the demo content with Tailwind layout classes

Validation

• GitHub Actions CI / quality passed for head 3513e748ded6be12b6f643018bde7822f0d0542a.
• Passed steps: npm run lint:ui, npm run typecheck:ui, npm run test:ui, npm run build:ui, npm run build:docs.
• Test run included updated src/components/feedback/overlays/Drawer/Drawer.test.tsx coverage for Tab and Shift+Tab focus looping.
• Not run locally: the Codex shell executor is currently failing with Failed to create unified exec process: No such file or directory.

Notes

• codebase-memory-mcp graph tools were not exposed in this session, so this run used repository files through GitHub as the AGENTS.md fallback.
• This branch starts from current main at 11041bb72fcca72ae77d23b74ac912fc09b23bfd and avoids the still-open Carousel PR fix(ui): add carousel rotation control #82 and ImagePreview PR fix(ui): improve image preview accessibility #83.

[ecc-tools]

ECC bundle files are already tracked in this repository. Skipping generation of another bundle PR.