refactor: unify browser error classification and deduplicate retry logic

[jackwener]

Summary

• Replace two overlapping error classification systems (isTransientBrowserError + isRetryableSettleError) with a single classifyBrowserError() that returns { retryable, delayMs }
• Deduplicate sendCommand() / sendCommandFull() retry loop (44 lines of identical code) into sendCommandRaw()

Design change

Before: two separate systems answering the same question ("is this error transient?") with different pattern lists, different delay strategies, in different files.

After: one function, one pattern list, one place to maintain. Each error category carries its own retry delay:

Category	Patterns	Delay
Extension/daemon transient	Extension disconnected, attach failed, No window with id, etc.	1500ms
CDP target navigation	Inspected target navigated or closed, -32000 + target	200ms
Non-transient	Everything else	not retryable

Files changed

File	What changed
src/browser/errors.ts	New classifyBrowserError() → RetryAdvice; isTransientBrowserError() kept as convenience wrapper
src/browser/daemon-client.ts	Extract sendCommandRaw(), uses classifyBrowserError().delayMs instead of hardcoded 1500ms
src/browser/page.ts	Remove isRetryableSettleError(), use classifyBrowserError() with its delay advice
src/browser/errors.test.ts	Tests for all error categories with delay assertions
src/browser.test.ts	Updated to test unified classification

Test plan

• 594 tests pass, 0 failures
• TypeScript compiles clean
• isTransientBrowserError() still works (backward compat wrapper)
• Pipeline executor unchanged — still imports isTransientBrowserError from errors.ts