feat(browser): wire transport faults into scenarios

[chubes4]

Summary

• expose the canonical transport-fault model through public browser actions and scenarios
• preserve preview routing/network policy, block service-worker bypass, and isolate schedules per browser context
• publish secret-safe matched/consumed/unmatched evidence with bounded teardown and structural replay identity

Fidelity

• browser HTTP(S) routing is supported for navigation, fetch, XHR, and subresources with service workers blocked
• server-side WordPress HTTP traffic remains owned by the existing WordPress HTTP adapter
• timeout, refusal, reset, malformed response, and truncation are Playwright-level emulations rather than socket-level faults
• Playwright cannot cancel an underlying route.fetch; bounded teardown reports remaining fetches and timed-out honestly

Testing

• npm run build
• npm run test:adversarial-runtime (21 passed)
• npm run test:browser-scenarios
• PLAYWRIGHT_BROWSERS_PATH=/home/opencode/.cache/ms-playwright npm run test:browser-actions-environment (9 passed)
• PLAYWRIGHT_BROWSERS_PATH=/home/opencode/.cache/ms-playwright npm run test:browser-transport-faults (5 passed)
• npm run test:recipe-validation-descriptors
• git diff --check

Closes #2208