Enhance activation orb effect

[acgxv]

Context: Floating panel notes list deferred enhancements for the activation orb effect.

Scope:

• Explore higher particle density, spark trails, or audio-reactive intensity.
• Keep the effect elegant and non-dominant.

Reference: docs/guide/development/ui_floating_panel_notes.md (Deferred enhancements).

Acceptance:

• One or more enhancements implemented or prototyped.
• Visual impact and performance considerations documented.