feat(patterns): merge pattern styles and add mode support

Consolidate legacy pattern ids into meteor, particles, sparkle, chase,
and colour_cycle with n6/mode style selection; add pattern_modes helper,
self-contained tests/all.py, and preset mode alias on wire.

Co-authored-by: Cursor <cursoragent@cursor.com>

src/preset.py

@@ -27,6 +27,7 @@ class Preset:
             "brightness": "b",
             "auto": "a",
             "background": "bg",
+            "mode": "n6",
         }
         int_fields = {"d", "b", "n1", "n2", "n3", "n4", "n5", "n6"}
         allowed_fields = {"p", "c", "d", "b", "a", "bg", "n1", "n2", "n3", "n4", "n5", "n6"}