docs: close remaining Island UI and content parity gaps

[Ethandasw]

Closes #108

Loop metadata

• Run ID: 20260724T132107Z-issue-108-743034
• Base SHA: 9eea05360a90e46a4c66c2e821e9ad5bd6c71c67
• Head SHA: c5100509fb33fc68ff36089c92cfb43c2ab22424
• Implementation SHA: 4b9818f7c2a77f4dea87c4eceb188bd41facb367
• Risk: Medium — broad documentation UI/content and browser-regression coverage; no package runtime, dependency, release, public API, workflow, package-manifest, or protected verification-plane changes.

Changes

• Restores Island shell behavior, Links destinations, Guide/About grouping, edit/pagination/footer affordances, and root locale routing.
• Restores bilingual guide hierarchy and 76 live component variants across 15 components with keyboard-accessible Preview/Code and source copy.
• Restores public API/data-attribute discoverability while retaining Echo UI 1.1.x, accessibility, lifecycle, error, and real-audio improvements.
• Adds a maintained Island parity matrix, allowed-path deterministic rendered-route contracts, content inventory assertions, and exact paired before/after evidence.
• Repairs the initial CI rejection by removing every protected root scripts/ diff and supplying 12 strict evidence pairs under the loop evidence path.

Acceptance criteria

• Island → Nextra parity matrix and intentional modern exceptions are documented.
• English/Chinese shell behavior is covered at desktop/mobile and light/dark combinations.
• Component variant/source coverage, API/data attributes, root behavior, edit/pagination/footer, and Links are regression-tested.
• Frozen-base before and exact-implementation after captures cover all required routes and interactions.

Verification

• pnpm vitest run tests/docs-parity.test.ts tests/docs-visual-contract.test.ts: passed (exit code 0)
• pnpm vitest run tests/docs-rendered-visual-contract.test.ts: passed (exit code 0)
• pnpm lint: passed (exit code 0)
• pnpm typecheck:docs: passed (exit code 0)
• pnpm build:docs: passed (exit code 0)
• pnpm test:docs: passed (exit code 0)
• pnpm verify: passed (exit code 0)
• node loops/issue-dev-loop/scripts/validate-candidate-control-plane.mjs --loop-root loops/issue-dev-loop --run-id 20260724T132107Z-issue-108-743034 --base-sha 9eea05360a90e46a4c66c2e821e9ad5bd6c71c67 --head-sha 4b9818f7c2a77f4dea87c4eceb188bd41facb367: passed (exit code 0)

Evidence

Representative before/after comparisons are embedded below. All image URLs are pinned to exact Draft head c5100509fb33fc68ff36089c92cfb43c2ab22424.

Guide navigation, pagination, and footer

Before	After

Component Preview/Code and copy interaction

Before	After

Visualization and Links menu

Before	After

Hook real-audio state

Before	After

Remaining paired screenshot evidence (8 scenarios)

• Root locale routing: before · after
• About/WeChat: before · after
• Edit link: before · after
• Locale switch: before · after
• Mobile navigation: before · after
• Theme switch: before · after
• Keyboard/reduced motion: before · after
• Knob responsive layout: before · after

• Screenshot and interaction index
• Paired screenshot manifest
• Maintained Island parity matrix
• Low-privilege exact-head workflow artifact: pending the repaired Draft head run.

Independent review

Pending fresh-context Traviinam COMMENT-only review for exact head c5100509fb33fc68ff36089c92cfb43c2ab22424.

Known limitations

• Workflow run 30122020412 belongs to the superseded head and failed the protected-diff/evidence-pair gates; the repaired exact-head run must pass before owner notification.
• The trusted Git credential-helper argument-forwarding defect required owner-assisted branch pushes; it should be repaired separately in the trusted control plane before future loops.

This PR must be marked Ready, reviewed, and merged by @codeacme17. The loop has no Ready, approval, or merge authority.