feat(extension): reveal the selected component in Elements and open its source

[erkamyaman]

What and why

Selection only went one way, from the Elements panel to Components. This adds the other direction for #164.

• Page side: component-source.ts reads ɵcmp.debugInfo (filePath, 1-based lineNumber, dev builds only) into detail.source, and installs __pangularHostOf / __pangularClassOf helpers scoped to the page id, only when the components inspector is on. No DOM writes.
• Extension: panel-actions.js handles pangular:reveal-element (inspect(host)) and pangular:open-source (matches the file against getResources() and calls openResource, falling back to inspect(class)). Ids and page ids are validated, and only the UI frame on our origin can send.
• Panel: the Components detail header shows file:line (debugInfo first, then the source scan), plus Reveal in Elements and Open source buttons, only inside the extension with a connected page (not Angular Native or a static report). Failures show in a status line.
• Docs: components inspector, Chrome extension guide and the contributing extension page.

Refs #164

How it was verified

• pnpm commit:check, pnpm format:check, pnpm typecheck, pnpm skills:check
• pnpm test:devtools (1182) and pnpm test:panel (114)
• pnpm docs:build, pnpm test:axe
• pnpm extension:build and extension/ui committed
• Manual test in real Chrome (below), not done yet, which is why this is a draft

Manual test

1. pnpm build --configuration development && node dist/pangular-inspector/server/server.mjs, reload the unpacked extension/, open http://localhost:4000, then DevTools > Pangular Inspector > Components.
2. Select a component: the header shows src/app/...ts:N and the two buttons. Reveal in Elements should select its host in Elements.
3. Open source should open the .ts file at the export class line in Sources. If it's one line off, adjust line - 1 in extension/panel-actions.js; if compiled JS opens, getResources() doesn't list source-mapped files and the class fallback ran.
4. The buttons don't show at http://localhost:4000/__devframes/pangular/ in a normal tab.

Decisions to confirm

• Open source shows even without debugInfo, because the class fallback still works (the issue said to hide it).
• The buttons aren't gated by actions: they don't change app state, add no RPC or agent tool. They need the components inspector on.

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