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/strobe.sexp

@@ -1,4 +1,5 @@
 ;; Strobe effect - holds frames for choppy look
+(require-primitives "core")
 
 (define-effect strobe
   :params (
@@ -7,7 +8,7 @@
   (let* ((held (state-get 'held nil))
          (held-until (state-get 'held-until 0))
          (frame-duration (/ 1 frame_rate)))
-    (if (or (= held nil) (>= t held-until))
+    (if (or (core:is-nil held) (>= t held-until))
         (begin
           (state-set 'held (copy frame))
           (state-set 'held-until (+ t frame-duration))