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/primitive_libs/core.py

@@ -189,6 +189,30 @@ def prim_range(*args):
     return []
 
 
+# Random
+import random
+_rng = random.Random()
+
+def prim_rand():
+    """Return random float in [0, 1)."""
+    return _rng.random()
+
+def prim_rand_int(lo, hi):
+    """Return random integer in [lo, hi]."""
+    return _rng.randint(int(lo), int(hi))
+
+def prim_rand_range(lo, hi):
+    """Return random float in [lo, hi)."""
+    return lo + _rng.random() * (hi - lo)
+
+def prim_map_range(val, from_lo, from_hi, to_lo, to_hi):
+    """Map value from one range to another."""
+    if from_hi == from_lo:
+        return to_lo
+    t = (val - from_lo) / (from_hi - from_lo)
+    return to_lo + t * (to_hi - to_lo)
+
+
 # Core primitives dict
 PRIMITIVES = {
     # Arithmetic
@@ -231,10 +255,17 @@ PRIMITIVES = {
     'list?': prim_is_list,
     'dict?': prim_is_dict,
     'nil?': prim_is_nil,
+    'is-nil': prim_is_nil,
 
     # Higher-order / iteration
     'reduce': prim_reduce,
     'fold': prim_reduce,
     'map': prim_map,
     'range': prim_range,
+
+    # Random
+    'rand': prim_rand,
+    'rand-int': prim_rand_int,
+    'rand-range': prim_rand_range,
+    'map-range': prim_map_range,
 }