Add modular primitive libraries and fix Symbol class compatibility

- Add primitive_libs/ with modular primitive loading (core, math, image,
  color, color_ops, filters, geometry, drawing, blending, arrays, ascii)
- Effects now explicitly declare dependencies via (require-primitives "...")
- Convert ascii-fx-zone from hardcoded special form to loadable primitive
- Add _is_symbol/_is_keyword helpers for duck typing to support both
  sexp_effects.parser.Symbol and artdag.sexp.parser.Symbol classes
- Auto-inject _interp and _env for primitives that need them
- Remove silent error swallowing in cell_effect evaluation

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

sexp_effects/effects/invert.sexp

@@ -1,6 +1,8 @@
 ;; Invert effect - inverts all colors
 ;; Uses vectorized invert-img primitive for fast processing
 
+(require-primitives "color_ops")
+
 (define-effect invert
   :params ()
   (invert-img frame))