feat(browser): attach to a running Chrome session via direct CDP

[seichris]

Cherry-picks steipete#119 into this fork.

Summary

• add a local browser-attach-running path for attaching Oracle to an already-running Chromium session
• connect directly over CDP and open a dedicated Oracle-owned tab in the existing browser session
• extend session, reattach, config, docs, and tests for the new attach-running flow

Why
This avoids stale or missing cookies in temporary automation profiles and makes browser mode much more practical when the user is already signed in to ChatGPT in their normal browser.

Validation

• upstream PR notes: pnpm vitest run tests/browser/attachRunning.test.ts tests/browser/chromeLifecycle.test.ts
• upstream PR notes: pnpm build
• upstream PR notes: pnpm vitest run --exclude tmp/** tests/browser tests/cli/browserConfig.test.ts tests/cli/browserDefaults.test.ts tests/cli/sessionRunner.test.ts
• not rerun in this checkout because local dependencies are not installed