Add composable ASCII art with per-cell effects and explicit effect loading

Implements ascii_fx_zone effect that allows applying arbitrary sexp effects
to each character cell via cell_effect lambdas. Each cell is rendered as a
small image that effects can operate on.

Key changes:
- New ascii_fx_zone effect with cell_effect parameter for per-cell transforms
- Zone context (row, col, lum, sat, hue, etc.) available in cell_effect lambdas
- Effects are now loaded explicitly from recipe declarations, not auto-loaded
- Added effects_registry to plan for explicit effect dependency tracking
- Updated effect definition syntax across all sexp effects
- New run_staged.py for executing staged recipes
- Example recipes demonstrating alternating rotation and blur/rgb_split patterns

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

constructs/cycle-effects-preset.sexp

@@ -8,8 +8,13 @@
 ;; Binding specs {:bind "analyzer" :range [min max]} are resolved to actual bindings
 
 (define-construct cycle-effects-preset
-  "Cycle through effects from a data preset, with automatic binding resolution"
-  ()
+  :params (
+    (preset :type any :desc "List of effect preset definitions")
+    (videos :type any :desc "List of video source nodes")
+    (video_infos :type any :desc "List of video info analysis results")
+    (beats :type any :desc "Beat analysis data with :times")
+    (beats_per_segment :type int :default 4 :desc "Number of beats per segment")
+  )
   (let [num-effects (len preset)
         num-videos (len videos)
         ;; Extract durations from video-info analysis results