Add project documentation: design spec, implementation plan, and progress tracking

Initial project setup with README, CLAUDE.md (AI dev context), DESIGN.md
(full technical design covering architecture, data model, coordinate system,
rendering strategy), PROJECT_PLAN.md (phased implementation steps), and
PROGRESS.md (completion tracking).

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

PROJECT_PLAN.md

@@ -0,0 +1,120 @@
+# PROJECT_PLAN.md — eng-pad Implementation Steps
+
+This file tracks all implementation steps. Check off steps as they are
+completed and log them in PROGRESS.md.
+
+## Phase 0: Project Documents
+
+- [x] 0.1: Create DESIGN.md
+- [x] 0.2: Create PROJECT_PLAN.md (this file)
+- [x] 0.3: Create PROGRESS.md
+- [x] 0.4: Update CLAUDE.md with build commands and source tree
+
+## Phase 1: Project Skeleton + Data Layer
+
+- [ ] 1.1: Generate Android project with Gradle
+  - `build.gradle.kts` (root), `app/build.gradle.kts`, `settings.gradle.kts`
+  - Kotlin, Compose, Room KSP, minSdk 30, targetSdk 34
+- [ ] 1.2: Configure `gradle/libs.versions.toml` version catalog
+  - Compose BOM, Room, Navigation, Lifecycle, Coroutines
+- [ ] 1.3: Configure linting (`app/build.gradle.kts` Android Lint config)
+- [ ] 1.4: Define Room entities
+  - `data/model/Notebook.kt`, `Page.kt`, `Stroke.kt`, `PageSize.kt`
+- [ ] 1.5: Implement type converters
+  - `data/db/Converters.kt` — `FloatArray` ↔ `ByteArray`, `PageSize` ↔ `String`
+- [ ] 1.6: Define DAOs
+  - `data/db/NotebookDao.kt`, `PageDao.kt`, `StrokeDao.kt`
+- [ ] 1.7: Define Room database
+  - `data/db/EngPadDatabase.kt`
+- [ ] 1.8: Implement repositories
+  - `data/repository/NotebookRepository.kt`, `PageRepository.kt`
+- [ ] 1.9: Unit tests
+  - `test/.../data/StrokeBlobTest.kt` — blob roundtrip
+  - `test/.../data/RepositoryTest.kt` — CRUD, cascade delete
+- **Verify:** `./gradlew build && ./gradlew test && ./gradlew lint`
+
+## Phase 2: Notebook List Screen
+
+- [ ] 2.1: Set up `MainActivity` with Compose and `NavHost`
+  - `MainActivity.kt`, `ui/navigation/NavGraph.kt`, `ui/theme/Theme.kt`
+- [ ] 2.2: Implement `NotebookListViewModel`
+  - `ui/notebooks/NotebookListViewModel.kt`
+- [ ] 2.3: Implement `NotebookListScreen`
+  - `ui/notebooks/NotebookListScreen.kt` — list, create dialog, delete
+- [ ] 2.4: Auto-create page 1 on notebook creation
+  - In `NotebookRepository` or ViewModel
+- [ ] 2.5: Navigation: tap notebook → page list (stub screen)
+- **Verify:** `./gradlew build && ./gradlew test`
+
+## Phase 3: Canvas — Basic Drawing
+
+- [ ] 3.1: Implement `PadCanvasView` — stylus event handling
+  - `ui/editor/PadCanvasView.kt` — `onTouchEvent`, `getHistoricalX/Y`
+- [ ] 3.2: Stroke rendering — `Path`/`Paint`, backing bitmap
+- [ ] 3.3: Grid drawing — 14.4pt spacing, toggleable
+- [ ] 3.4: Coordinate transform — canonical ↔ screen via `Matrix`
+- [ ] 3.5: Implement `CanvasState`
+  - `ui/editor/CanvasState.kt` — zoom, pan, active tool
+- [ ] 3.6: Implement `EditorViewModel`
+  - `ui/editor/EditorViewModel.kt` — load/save strokes from Room
+- [ ] 3.7: Implement `EditorScreen` + toolbar
+  - `ui/editor/EditorScreen.kt`, `ui/editor/Toolbar.kt`
+- [ ] 3.8: Wire navigation from notebook/page list to editor
+- **Verify:** `./gradlew build && ./gradlew test` + manual on-device test
+
+## Phase 4: Zoom and Pan
+
+- [ ] 4.1: `ScaleGestureDetector` for pinch-to-zoom (0.5×–4×)
+- [ ] 4.2: Finger drag for pan with bounds clamping
+- [ ] 4.3: Input routing — stylus → draw, finger → zoom/pan
+- **Verify:** manual on-device test
+
+## Phase 5: Eraser
+
+- [ ] 5.1: Eraser mode in `CanvasState`
+- [ ] 5.2: Hit testing — bounding box pre-filter + point distance
+- [ ] 5.3: Stroke deletion + backing bitmap rebuild
+- **Verify:** `./gradlew test` + manual test
+
+## Phase 6: Undo/Redo
+
+- [ ] 6.1: `UndoableAction` interface + concrete actions
+  - `undo/UndoableAction.kt`
+- [ ] 6.2: `UndoManager` — undo/redo stacks, depth 50
+  - `undo/UndoManager.kt`
+- [ ] 6.3: Integrate with `EditorViewModel` + toolbar
+- [ ] 6.4: Unit tests — `test/.../undo/UndoManagerTest.kt`
+- **Verify:** `./gradlew test` + manual test
+
+## Phase 7: Selection — Move, Copy, Delete
+
+- [ ] 7.1: Selection mode — rectangle selection
+- [ ] 7.2: Visual feedback — highlight, bounding box
+- [ ] 7.3: Operations — delete, drag-to-move, copy/paste
+- [ ] 7.4: Undo integration for all selection operations
+- **Verify:** `./gradlew test` + manual test
+
+## Phase 8: Multi-Page Navigation
+
+- [ ] 8.1: `PageListScreen` with thumbnails
+  - `ui/pages/PageListScreen.kt`, `PageListViewModel.kt`
+- [ ] 8.2: Add new page button
+- [ ] 8.3: Prev/next page navigation in editor + auto-save
+- **Verify:** manual test
+
+## Phase 9: PDF Export
+
+- [ ] 9.1: `PdfExporter` — Android `PdfDocument` API
+  - `ui/export/PdfExporter.kt`
+- [ ] 9.2: Share via `Intent.ACTION_SEND` + `FileProvider`
+  - `res/xml/file_provider_paths.xml`, `AndroidManifest.xml` updates
+- [ ] 9.3: Export button in toolbar (per-page + whole notebook)
+- [ ] 9.4: Unit test — verify PDF generation
+- **Verify:** `./gradlew test` + open exported PDF, confirm no grid
+
+## Phase 10: Polish
+
+- [ ] 10.1: E-ink optimizations — minimize animations, high contrast
+- [ ] 10.2: Auto-save zoom/pan state per page
+- [ ] 10.3: Empty states, error handling, delete confirmations
+- [ ] 10.4: Performance profiling on target devices