Libraries panel, 2 more examples, stop tracking outputs/

[vecnode]

What & why

1. Stop tracking outputs/

Generated sketches, PNG captures, and WebM recordings are local. Added outputs/* to .gitignore (keeping outputs/README.md as the folder placeholder) and removed the four old test .js files from tracking (kept on disk). The app re-creates outputs/ at runtime.

2. Two more examples

Added Random walker and Particle swarm to the Examples menu (5 total). Selecting one loads and runs it.

3. Libraries panel (relates to #3)

New Libraries section in the right side panel, under Capture:

• A dropdown of p5.js builds, populated from a new public/libraries.json manifest ({ id, name, version, url, isLocal }). The manifest doubles as the allow-list of injectable builds — the JS-first approach proposed in Proposal: JS-First Library Injection Architecture (replace C++ LibraryRegistry) #3.
• An inline Apply button. Applying sets activeLibrary, so future sketch runs load that build's <script>, reloads any running sketch, and updates the version label under the editor to the chosen build.
• The bundled v1.11.3 (isLocal: true) is the default and keeps the app fully offline. The three online options load p5 from cdnjs — trading offline-first for version flexibility, loaded inside the same sandboxed, opaque-origin iframe (no access to the parent page or local API).

Reviewer notes

• node --check passes; libraries.json is valid JSON; the Debug target builds and re-embeds assets.
• Smoke-tested at runtime: GET /libraries.json returns 200 with all four entries.
• Online builds require a network connection; selecting one when offline will make the sketch fail to find p5 (surfaced as a sketch error). The default stays offline.
• Styling reuses the existing panel tokens (select + inline button match the panel buttons).

🤖 Generated with Claude Code