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/trails.sexp

@@ -1,4 +1,5 @@
 ;; Trails effect - persistent motion trails
+(require-primitives "image" "blending")
 
 (define-effect trails
   :params (
@@ -10,10 +11,10 @@
         (begin
           (state-set 'buffer (copy frame))
           frame)
-        (let* ((faded (blend-images buffer
-                                    (make-image (width frame) (height frame) (list 0 0 0))
+        (let* ((faded (blending:blend-images buffer
+                                    (make-image (image:width frame) (image:height frame) (list 0 0 0))
                                     (- 1 persistence)))
-               (result (blend-mode faded current "lighten")))
+               (result (blending:blend-mode faded current "lighten")))
           (begin
             (state-set 'buffer result)
             result)))))