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/standard-primitives.sexp

@@ -0,0 +1,14 @@
+;; Standard Primitives Bundle
+;;
+;; Loads all commonly-used primitive libraries.
+;; Include this at the top of streaming recipes.
+;;
+;; Usage:
+;;   (include :path "../templates/standard-primitives.sexp")
+
+(require-primitives "geometry")
+(require-primitives "core")
+(require-primitives "image")
+(require-primitives "blending")
+(require-primitives "color_ops")
+(require-primitives "streaming")