[codex] Improve browser bridge connection errors

[961882]

Summary

Improve BROWSER_CONNECT failures for Browser Bridge extension disconnects.

This change makes browser connection failures easier for both humans and automation to diagnose by surfacing the existing connection kind in structured error output and by recommending the lower-risk recovery path first.

What changed

• Add machine-readable kind, layer, and recovery fields to BrowserConnectError envelopes.
• Classify extension disconnects as the browser_bridge layer.
• Prefer extension reload guidance before daemon restart guidance when the daemon is running but the extension is disconnected.
• Update doctor messaging for extension-disconnected states.
• Add unit coverage for the structured error fields and updated recovery hint.

Root cause

BrowserConnectError already tracked a coarse failure kind internally, but the CLI error envelope only exposed the generic BROWSER_CONNECT code. As a result, agents and scripts had to infer whether the failure was in daemon startup, extension connection, or command execution.

The human hint also jumped too quickly to daemon restart guidance, even when the lower-risk fix is reloading the already-installed OpenCLI extension in chrome://extensions.

User impact

Normal successful commands remain unchanged.

On failure, users and agents get clearer, more actionable information:

• kind: extension-not-connected
• layer: browser_bridge
• safe recovery steps such as reloading the OpenCLI extension and retrying once
• manual recovery steps such as running opencli doctor

Validation

• npm test -- src/errors.test.ts src/browser.test.ts src/doctor.test.ts
• npm run typecheck