docs: add more-patterns OpenSpec change

Plan 6 additional built-in patterns mapped to digit keys 5-0.

openspec/changes/more-patterns/design.md

@@ -0,0 +1,30 @@
+# Design
+
+## Context
+
+Pattern module currently has 4 patterns with static offsets. Config maps digits 1-4.
+
+## Goals / Non-Goals
+
+**Goals:**
+- Add 6 patterns with correct offsets.
+- Extend default config digits 5-0.
+
+**Non-Goals:**
+- Pattern editor.
+- Loading from files.
+
+## Decisions
+
+### D1: Pattern storage
+- Add static offset arrays and entries in `patterns[]`.
+
+### D2: Key mapping
+- 5=Beacon, 6=Loaf, 7=Boat, 8=Tub, 9=R-pentomino, 0=Acorn.
+
+### D3: Config enum
+- Add `ACTION_SELECT_BEACON` etc. or refactor? Use new enum values for minimal change.
+
+## Open Questions
+
+None.