Add --user-data-dir option for persistent Chrome profiles

[ryaker]

Summary

Enables agents (Claude, Gemini, and other browser automation tools) to run with persistent Chrome profiles instead of ephemeral blank contexts. This is essential for workflows requiring saved credentials, session state, and multi-account coordination.

Changes

• src/types.ts: Added userDataDir?: string to LaunchCommand interface
• src/browser.ts: Modified launch() method to use launchPersistentContext() when userDataDir is specified
• README.md: Added --user-data-dir option documentation and usage examples
• Documentation: Comprehensive examples for multi-profile and multi-agent scenarios

Key Features

For Users:

• One-time profile setup, then agents access saved credentials automatically
• No manual login flows between runs
• Different agents can use different profiles simultaneously

For Agents:

• Deterministic profile selection via --user-data-dir or AGENT_BROWSER_USER_DATA_DIR environment variable
• Full access to cookies, localStorage, saved passwords
• Session isolation via --session flag for parallel execution
• Works in headless mode (no GUI required)

Use Cases

1. Multi-account workflows: Different Google accounts or work contexts in parallel
2. Saved credentials: Skip login flows by using authenticated profiles
3. Session persistence: Maintain cookies and localStorage across multiple runs
4. Profile-specific data: Access extensions, preferences, and custom settings

Testing

✓ Tested with custom temporary profile directories
✓ Tested with 3 real Chrome profiles (Default, Profile 1, Profile 2)
✓ Backward compatibility verified (existing code without userDataDir works unchanged)
✓ Build and type checking pass

Example Usage

# Use a specific Chrome profile
AGENT_BROWSER_USER_DATA_DIR="$HOME/Library/Application Support/Google/Chrome/Profile 1" \
  agent-browser open gmail.com

# Two agents with different profiles (parallel execution)
AGENT_BROWSER_SESSION=agent-personal \
  AGENT_BROWSER_USER_DATA_DIR="$HOME/Library/Application Support/Google/Chrome/Default" \
  agent-browser open gmail.com &

AGENT_BROWSER_SESSION=agent-work \
  AGENT_BROWSER_USER_DATA_DIR="$HOME/Library/Application Support/Google/Chrome/Profile 1" \
  agent-browser open company-app.com

🤖 Generated with Claude Code

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Additional Suggestions:

1. The Rust CLI flags parser doesn't support the --user-data-dir flag that is documented in the README and implemented in the Node.js backend

2. The launchSchema in protocol.ts doesn't include userDataDir field validation, even though the LaunchCommand interface in types.ts defines it

3. The daemon.ts auto-launch browser initialization doesn't pass the AGENT_BROWSER_USER_DATA_DIR environment variable to browser.launch()