feat(cli): add media commands for audio/video playback control

[mvanhorn]

Summary

Add media commands to detect and control audio/video playback state on the page.

• agent-browser media status - list all media elements with playing/paused state, currentTime, duration
• agent-browser media pause - pause all playing media
• agent-browser media play - resume all paused media

Closes #644

Evidence

Signal	Source
Issue #644	"Feature request: add audio/sound support for media playback verification" - 11 reactions, maintainer said "we'll definitely consider this"
No prior PR	First focused implementation
YouTube	"Agent Browser: The CLI That Gives AI Agents Eyes on the Web" - media testing noted as gap
Issue #66	Video recording support request

Implementation

Uses Runtime.evaluate with JavaScript that queries all <audio> and <video> elements. For status, reads paused, currentTime, duration, volume, muted, loop, and src. For play/pause, calls the native .play() / .pause() methods.

Files changed

• cli/src/commands.rs - media command parser with status/pause/play subcommands
• cli/src/native/actions.rs - three CDP handlers using Runtime.evaluate
• cli/src/output.rs - human-readable output for media status and play/pause results

Test plan

• cargo fmt passes
• cargo clippy passes
• cargo test passes (477 tests, 0 failures)
• Manual: agent-browser media status on page with video
• Manual: agent-browser media pause pauses playback
• Manual: agent-browser media play resumes playback

This contribution was developed with AI assistance (Claude Code).

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