fix(islands): wrap every client island in ErrorBoundary, not just AppIsland

[nastaso]

What does this PR do?

Closes #70. Reuses the existing ErrorBoundary (no new component, no new dependency) and wraps every top-level client island root, so a render throw in any island degrades to the existing recovery card and logs via logError, instead of blanking the region silently.

Wrapped (first pass, matching #70's own list): CertDashboardIsland, HeaderInteractive, FooterIsland, DonateButtonIsland, CookieConsentIsland, AccountLinkNoticeIsland.

Wrapped (second pass, after a codex adversarial audit found #70's own list was incomplete): AuthLinkNotice (index.astro), DomainProgressStrip ([domain].astro), BlogShareButton (BlogLayout.astro), AnalyticsBootstrap (BaseLayout.astro). None of these four were named in #70 - I verified them with a full repo grep for every client:only/client:idle/client:load mount in src/, which turned up exactly these 4 gaps and no more.

Already had it, untouched:

• AppIsland (pre-existing, the boundary fix(islands): wrap every client island in ErrorBoundary, not just AppIsland #70 was modeled on).
• StatsIsland - checked before wrapping and it's already been boundary-wrapped since PR fix(stats,history): cert ordering, error-state chips, single loader, shift-free stats swap (S1/S2/H2 + FLASH F2/F3) #145. Issue fix(islands): wrap every client island in ErrorBoundary, not just AppIsland #70 listed it as unprotected; that's stale as of fix(stats,history): cert ordering, error-state chips, single loader, shift-free stats swap (S1/S2/H2 + FLASH F2/F3) #145, so I left it alone rather than double-wrap.

No island hydration directives (client:idle/client:only) or island logic changed anywhere - only an import + a JSX wrap around each existing return (or, for the 4 multi-early-return components, a rename-and-wrap: the original function becomes an unexported *Inner, and the exported name becomes a thin <ErrorBoundary> wrapper around it, so no internal branching had to be touched).

Notes

• CookieConsentIsland is currently unmounted in BaseLayout.astro (dormant - see the comment above the GA script block). The wrap is harmless and future-proofs it; no live effect today.
• AnalyticsBootstrap always renders null - the wrap still protects against a synchronous render-phase throw before that return, for consistency with every other island's policy.

Testing

This repo's vitest environment is node (no DOM) and has no react-test-renderer / @testing-library/react (AGENTS.md: no new dependencies). I checked both renderToStaticMarkup and renderToPipeableStream by hand before writing the test - neither recovers inline from a synchronous root-level throw the way the client reconciler does, so an end-to-end "mount and throw" test isn't possible here without a new dependency.

Instead src/components/ErrorBoundary.test.tsx drives ErrorBoundary's own lifecycle methods directly (getDerivedStateFromError, componentDidCatch, render()) - the exact methods React itself calls - and asserts on the returned element tree. Mutation-tested by hand: changed render() to always return children regardless of hasError, confirmed the "renders the recovery card instead of blanking" test goes red, reverted, confirmed green again.

• npm run check (typecheck + lint + unit tests): 0 errors, 0 warnings, 304/304 tests pass (added 4).
• npm run build: full guard chain green (citation, internal-graph, person-graph, check:seo-head, csp:hash, cf:headers).
• PW_PORT=4399 PW_REUSE_SERVER=0 npm run e2e: 109/109 non-skipped tests pass (20 skipped need real Supabase creds, same as baseline) - re-run after the second-pass fixes too.

Checklist

• npm run check passes locally
• npm run build passes locally (full guard chain)
• npm run e2e passes locally (isolated port)
• No new third-party dependencies
• No changes to island hydration directives or island logic - only the ErrorBoundary wrap

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