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>

sexp_effects/effects/scanlines.sexp

@@ -1,4 +1,5 @@
 ;; Scanlines effect - VHS-style horizontal line shifting
+(require-primitives "core")
 
 (define-effect scanlines
   :params (
@@ -9,6 +10,6 @@
   (map-rows frame
     (lambda (y row)
       (let* ((sine-shift (* amplitude (sin (/ (* y 6.28) (max 1 frequency)))))
-             (rand-shift (random (- amplitude) amplitude))
+             (rand-shift (core:rand-range (- amplitude) amplitude))
              (shift (floor (lerp sine-shift rand-shift randomness))))
         (roll row shift 0)))))