docs: add plugin demo videos

[omercnet]

Summary

• add a native GitHub video attachment to each of the 12 plugin READMEs
• let GitHub render each MP4 inline with controls
• let paseo.cafe discover the same user-attachment URLs and embed them automatically
• keep generated MP4s and posters out of repository history

Attachment inventory: #180 (comment)

Verification

• uploaded all 12 MP4s with gh pr comment --attach
• verified a user-attachment URL responds as video/mp4
• verified GitHub GFM renders the bare URL as a native <video> player
• validated all 12 URLs against paseo.cafe's GitHub attachment detector
• ran git diff --check

No runtime code changed.

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[omercnet]

README demo video attachments

Tell Agent

tell-agent.mp4

Queens

queens.mp4

PR Radar

pr-radar.mp4

Shared Browser

paseo-shared-browser.mp4

Paseo OMP

paseo-omp.mp4

Gas City

paseo-gas-city.mp4

Paseo Beads

paseo-beads.mp4

Paseo Dracula

paseo-dracula.mp4

Fresh Worktrees

fresh-worktrees.mp4

Context Mode

context-mode.mp4

Agent Crew

agent-crew.mp4

Agent Monitor

agent-monitor.mp4