Replace example shows with numbered production shows and add sparkle flag

- Rename all show .txt files with NNN_ numeric prefix so order is explicit
  and controlled by filename (001_heartbeat_red through 006_party)
- Drop HOME_SHOW special-casing from convert_all.py; show 0 is simply the
  lowest-numbered file
- Add SHOW_FLAG_SPARKLE support: shows can declare '// flags: sparkle' to
  overlay random white flashes on top of the base color each frame
- Wire sparkle into led_controller and config.h (SPARKLE_CHANCE/FRAMES)
- Replace old placeholder/example shows with the six production shows

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

arduino/cosplay_lights/config.h

@@ -43,6 +43,14 @@
 
 // -- Active pattern ------------------------------------------
 // Controls how the current color is mapped to the LEDs.
-// Only PATTERN_SOLID is included; see DETAILS.md for adding more.
+// See DETAILS.md for adding more patterns.
 #define PATTERN_SOLID  0
 #define ACTIVE_PATTERN PATTERN_SOLID
+
+// -- Sparkle tuning ------------------------------------------
+// Applied to shows that have the SHOW_FLAG_SPARKLE flag set.
+// SPARKLE_CHANCE : 0–255 probability of a new sparkle each frame (~60fps).
+//                  80 ≈ 31%, giving roughly 2–3 simultaneous sparkles on 60 LEDs.
+// SPARKLE_FRAMES : how many frames each sparkle stays white (1 frame ≈ 16ms).
+#define SPARKLE_CHANCE 80
+#define SPARKLE_FRAMES 6