docs: Add subprocess integration guide with permission workarounds

[hnshah]

Summary

Adds comprehensive integration guide for using Peekaboo from subprocess contexts (Node.js, OpenClaw, etc.) with workarounds for Bridge permission issues.

Fixes #77

Problem

Users report permission errors when running Peekaboo capture commands from subprocess contexts, despite macOS permissions being granted. This occurs because:

1. Peekaboo v3 routes commands through a Bridge daemon
2. Bridge doesn't inherit TCC grants when spawned from subprocesses
3. ScreenCaptureKit requires per-process Screen Recording permission
4. Users aren't aware of the --no-remote flag workaround

Solution

Created docs/integrations/subprocess.md documenting:

• Why it happens: Bridge architecture + macOS TCC per-process grants
• How to fix it: Use --no-remote --capture-engine cg flags
• Code examples: Node.js wrappers with error handling
• Performance notes: CoreGraphics vs ScreenCaptureKit tradeoffs
• Complete workflow: Capture → Find element → Click example
• Troubleshooting: Common errors and solutions

Changes

• ✅ New docs/integrations/subprocess.md (235 lines)
• ✅ New docs/integrations/README.md (integration hub)
• ✅ Tested workaround in Node.js subprocess context
• ✅ All code examples verified working

Testing

# Verified workaround works from subprocess
node -e "
const { execSync } = require('child_process');
const result = execSync('peekaboo see --app Finder --no-remote --capture-engine cg --json', {encoding: 'utf8'});
console.log(JSON.parse(result).success);
"
# Output: true

Impact

• Solves peekaboo no permission in openclaw. #77 (OpenClaw permission errors)
• Helps all users running Peekaboo from subprocesses
• Provides reusable Node.js integration patterns
• Documents performance tradeoffs clearly

Future Work (Optional)

Happy to implement in follow-up PRs if desired:

1. Auto-detection: CLI detects subprocess context and auto-uses local mode
2. Flag alias: --local → --no-remote --capture-engine cg
3. Better errors: Suggest --no-remote when Bridge fails
4. Environment variable: PEEKABOO_FORCE_LOCAL=1

Let me know if any of these would be helpful!

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Checklist:

• Created comprehensive integration guide
• Tested all code examples
• Verified workaround solves reported issue
• Added troubleshooting section
• Documented performance considerations