Remove dev/playwright_agent directory (#524)

Security issue: Hardcoded RunPod API credentials were committed in plaintext
at lines 31-32 of playwright_agent.py (RUNPOD_BASE_URL and RUNPOD_API_KEY).

This directory contained experimental code that is not actively being worked on.
Removing it addresses the credential exposure and reduces maintenance burden.

The exposed API key has been verified as already rotated/invalidated.

Reported by: Sahil Siddiki

Co-authored-by: Cursor Bot <bot@cursor.com>

Author: corbt