Add generic streaming interpreter with configurable sources/audio

- Add stream_sexp_generic.py: fully generic sexp interpreter
- Add streaming primitives for video sources and audio analysis
- Add config system for external sources and audio files
- Add templates for reusable scans and macros
- Fix video/audio stream mapping in file output
- Add dynamic source cycling based on sources array length
- Remove old Python effect files (migrated to sexp)
- Update sexp effects to use namespaced primitives

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

templates/scan-oscillating-spin.sexp

@@ -0,0 +1,28 @@
+;; Oscillating Spin Scan
+;;
+;; Accumulates rotation angle on each beat, reversing direction
+;; periodically for an oscillating effect.
+;;
+;; Required context:
+;;   - music: audio analyzer from (streaming:make-audio-analyzer ...)
+;;
+;; Provides scan: spin
+;;   Bind with: (bind spin :angle)  ;; cumulative rotation angle
+;;
+;; Behavior:
+;;   - Rotates 14.4 degrees per beat (completes 360 in 25 beats)
+;;   - After 20-30 beats, reverses direction
+;;   - Creates a swinging/oscillating rotation effect
+;;
+;; Usage:
+;;   (include :path "../templates/scan-oscillating-spin.sexp")
+;;
+;; In frame:
+;;   (rotate frame :angle (bind spin :angle))
+
+(scan spin (streaming:audio-beat music t)
+  :init {:angle 0 :dir 1 :left 25}
+  :step (if (> left 0)
+          (dict :angle (+ angle (* dir 14.4)) :dir dir :left (- left 1))
+          (dict :angle angle :dir (* dir -1)
+                :left (+ 20 (mod (streaming:audio-beat-count music t) 11)))))