Replace the demo with an SVG animation and cut the SketchyBar docs

[pszypowicz]

What's here

Three commits, each droppable on its own:

1. Replace the demo GIFs with an SVG animation - a single looping SMIL animation (docs/images/how-it-works.svg) shows the story side by side: AirPods connect, both panels get hijacked, the MicGuard panel snaps back with a shield pulse while the unprotected one stays on AirPods. Pure SMIL, no JS, so it animates inside GitHub READMEs and on the docs site. Replaces the four GIF/MP4 files. Used by both README.md and docs/index.md.
2. Remove the SketchyBar integration docs - all SketchyBar references and examples are gone (integrations page, notifications page, CLI and debugging mentions, README feature bullet, screenshot). The integrations page now only documents the building blocks: the two notifications, the ping-on-start pattern, CLI commands for click handlers, and the pgrep health check.
3. Drop the screenshots section - the animation carries the demo now. If you'd rather keep the menubar/settings screenshots, drop this commit and they're back.

Notes

• I verified the animation by rendering frames at 1s / 3s / 5s with headless Chrome: idle, hijack, and diverged outcomes all display as intended. Preview the raw SVG in a browser to see the full loop (10s).
• Em dashes in the touched markdown files were normalized to plain hyphens in passing.