fix(browser): reflect real Browser Bridge connection state

[jackwener]

Summary

• move Browser Bridge connection failure reporting into the bridge layer so commands use the real connect path
• make opencli v1.6.7 doctor (node v25.2.1)

[OK] Daemon: running on port 19825
[OK] Extension: connected (v1.6.7)
[OK] Connectivity: connected in 0.1s

Everything looks good! distinguish current daemon/extension state from unstable post-live-check flapping

• add unit coverage for typed Browser Bridge errors and doctor flaky-state reporting

Validation

• /Users/jakevin/code/opencli/node_modules/.bin/vitest run --project unit src/doctor.test.ts src/browser.test.ts src/execution.test.ts