Add WASD and mouse controller input support

[yondonfu]

Demo

2026-01-13.11-40-20.mp4

Summary

• Add controller input system for WASD keyboard and mouse capture via Pointer Lock API
• New controller-viz pipeline for testing/debugging controller inputs
• Frontend hook (useControllerInput) captures input and sends via WebRTC data channel
• Backend accumulates inputs pygame-style (keys=latest state, mouse=summed deltas)

Test plan

• Load controller-viz pipeline
• Click video to enable pointer lock
• Verify WASD/arrow keys light up directional indicators
• Verify mouse movement tracks red dot across canvas
• Press ESC to release pointer lock

Out of scope

• The logs spam "Output queue full..." with the controller-viz pipeline and will do so for any pipeline with a very high throughput (eg 60 fps). This will be addressed outside of this PR by updates to the consumer-producer pattern in the frame/pipeline processor logic.

🤖 Generated with Claude Code

[ryanontheinside]

lgtm