feat(renderer): add Canvas Lab with signals-driven 2D and WebGL2 panes

[simonhagger]

Summary

• New dependency-free Canvas Lab page (lab nav section, lazy route)
• 2D pane: animated sine-wave particle field via \CanvasRenderingContext2D\
• WebGL2 pane: live fragment-shader plasma quad tinted by accent signal
• Single rAF loop runs outside Angular change detection (zoneless-friendly); density/speed/accent/pause controls are signals read per frame
• GPU diagnostics: unmasked renderer string, max texture size, WebGPU availability probe
• Lifecycle hygiene: rAF cancel + ResizeObserver disconnect + \WEBGL_lose_context\ on destroy; DPR-aware resize

Validation

• Renderer production build green (Canvas Lab correctly excluded from prod route set by existing \�pp.routes.prod.ts\ design); dev build emits 27.77 kB lazy \canvas-lab-page\ chunk
• 
  enderer:test\ green including new create/teardown spec;
  enderer:lint\ green
• Live-verified in Electron dev app against renderer dev server on port 4210

Security Checklist

• Security review completed
• Threat model updated or N/A explained
• Confirmed no secrets/sensitive data present in committed files