Add Makefile with build, test, run, and devrun targets

Makefile wraps Gradle commands and adds emulator/device launch targets:
- run: builds, starts DC-1 emulator if needed, installs and launches
- devrun: builds, installs and launches on connected USB device
- Updated CLAUDE.md and DESIGN.md source trees

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

DESIGN.md

@@ -190,7 +190,7 @@ The editor toolbar controls the active mode:
    redrawn only when strokes change (add, delete, move).
 2. **In-progress stroke** (pen is down) is drawn directly to the canvas on
    each `onDraw` call, on top of the backing bitmap.
-3. **Grid** is drawn as a separate pass — thin gray lines at 14.4pt intervals.
+3. **Grid** is drawn as a separate pass — thin gray lines at 60pt intervals.
 4. The view `Matrix` transforms everything from canonical to screen space.
 
 This approach means `onDraw` is fast for the common case (pen moving):
@@ -317,14 +317,15 @@ eng-pad/
 │           └── kotlin/net/metacircular/engpad/
 │               ├── data/
 │               │   ├── StrokeBlobTest.kt             -- Float array ↔ blob roundtrip
-│               │   └── RepositoryTest.kt             -- CRUD + cascade delete
+│               │   └── PageSizeTest.kt               -- Page size enum tests
 │               └── undo/
 │                   └── UndoManagerTest.kt            -- Undo/redo logic
 ├── build.gradle.kts                                  -- Root build config
-├── settings.gradle.kts                               -- Project settings
+├── settings.gradle.kts                               -- Project settings (foojay JDK resolver)
 ├── gradle.properties                                 -- Gradle properties
 ├── gradle/
 │   └── libs.versions.toml                            -- Version catalog
+├── Makefile                                          -- Build targets (build, test, lint, run, devrun)
 ├── .gitignore
 ├── CLAUDE.md
 ├── README.md