feat: Linux support — LVGL filesystem fix + AppImage, add AppStore app manager

.github/workflows/ci.yml

@@ -43,7 +43,7 @@ jobs:
         uses: actions/cache@v4
         with:
           path: build
-          key: cmake-build-${{ runner.os }}-${{ hashFiles('CMakeLists.txt', 'cmake/**', 'crosspad-core', 'crosspad-gui') }}
+          key: cmake-build-${{ runner.os }}-${{ hashFiles('CMakeLists.txt', 'cmake/**', 'lib/crosspad-core', 'lib/crosspad-gui') }}
           restore-keys: cmake-build-${{ runner.os }}-
 
       - name: Configure

.github/workflows/release.yml

@@ -72,7 +72,7 @@ jobs:
           # Copy SDL2.dll from vcpkg installed dir
           cp "$RUNVCPKG_VCPKG_ROOT/installed/x64-windows/bin/SDL2.dll" dist/CrossPad/
           # Copy assets
-          cp -r crosspad-gui/assets dist/CrossPad/assets
+          cp -r lib/crosspad-gui/assets dist/CrossPad/assets
 
       - name: Upload artifact
         uses: actions/upload-artifact@v4
@@ -120,18 +120,44 @@ jobs:
       - name: Build
         run: cmake --build build
 
-      - name: Package
+      - name: Create AppImage icon
         run: |
-          mkdir -p dist/CrossPad
-          cp bin/CrossPad dist/CrossPad/CrossPad
-          chmod +x dist/CrossPad/CrossPad
-          cp -r crosspad-gui/assets dist/CrossPad/assets
+          python3 -c "
+          from PIL import Image
+          img = Image.open('logo.png')
+          img.thumbnail((256, 256), Image.LANCZOS)
+          new_img = Image.new('RGBA', (256, 256), (0, 0, 0, 0))
+          x = (256 - img.width) // 2
+          y = (256 - img.height) // 2
+          new_img.paste(img, (x, y))
+          new_img.save('CrossPad.png')
+          "
+
+      - name: Build AppImage
+        run: |
+          # Download linuxdeploy
+          wget -q https://github.com/linuxdeploy/linuxdeploy/releases/download/continuous/linuxdeploy-x86_64.AppImage
+          chmod +x linuxdeploy-x86_64.AppImage
+
+          # Prepare AppDir
+          mkdir -p AppDir/usr/bin
+          cp bin/CrossPad AppDir/usr/bin/CrossPad
+          chmod +x AppDir/usr/bin/CrossPad
+          cp -r lib/crosspad-gui/assets AppDir/usr/bin/assets
+
+          # Build AppImage
+          export OUTPUT=CrossPad-Linux-x86_64.AppImage
+          ./linuxdeploy-x86_64.AppImage \
+            --appdir=AppDir \
+            --desktop-file=CrossPad.desktop \
+            --icon-file=CrossPad.png \
+            --output=appimage
 
       - name: Upload artifact
         uses: actions/upload-artifact@v4
         with:
           name: CrossPad-Linux-x64
-          path: dist/CrossPad
+          path: CrossPad-Linux-x86_64.AppImage
 
   release:
     needs: [build-windows, build-linux]
@@ -149,11 +175,12 @@ jobs:
         with:
           name: CrossPad-Linux-x64
           path: CrossPad-Linux-x64
+          merge-multiple: true
 
       - name: Create archives
         run: |
           cd CrossPad-Windows-x64 && zip -r ../CrossPad-Windows-x64.zip . && cd ..
-          tar -czf CrossPad-Linux-x64.tar.gz -C CrossPad-Linux-x64 .
+          cp CrossPad-Linux-x64/CrossPad-Linux-x86_64.AppImage .
 
       - name: Checkout (for changelog generation)
         uses: actions/checkout@v4
@@ -209,7 +236,7 @@ jobs:
           prerelease: ${{ steps.tag.outputs.prerelease == 'true' }}
           files: |
             CrossPad-Windows-x64.zip
-            CrossPad-Linux-x64.tar.gz
+            CrossPad-Linux-x86_64.AppImage
 
       - name: Detect release type
         id: release_type

.gitignore

@@ -6,8 +6,10 @@ bin/
 .*/
 !.github/
 
-# VSCode
-.vscode
+# VSCode — ignore all except shared config
+.vscode/*
+!.vscode/settings.json
+!.vscode/tasks.json
 
 # MacOS file
 .DS_Store
@@ -23,3 +25,5 @@ _build_*.bat
 
 # Screenshots (dev/test artifacts)
 screenshots/
+app-registry.json
+apps.json

.gitmodules

@@ -8,8 +8,23 @@
 	path = FreeRTOS
 	url = https://github.com/FreeRTOS/FreeRTOS-Kernel.git
 [submodule "crosspad-core"]
-	path = crosspad-core
+	path = lib/crosspad-core
 	url = https://github.com/CrossPad/crosspad-core.git
 [submodule "crosspad-gui"]
-	path = crosspad-gui
+	path = lib/crosspad-gui
 	url = https://github.com/CrossPad/crosspad-gui.git
+[submodule "src/apps/crosspad-piano"]
+	path = src/apps/crosspad-piano
+	url = https://github.com/CrossPad/crosspad-piano.git
+[submodule "src/apps/crosspad-instructions"]
+	path = src/apps/crosspad-instructions
+	url = https://github.com/CrossPad/crosspad-instructions.git
+[submodule "src/apps/crosspad-appstore"]
+	path = src/apps/crosspad-appstore
+	url = https://github.com/CrossPad/crosspad-appstore.git
+[submodule "src/apps/crosspad-serial-monitor"]
+	path = src/apps/crosspad-serial-monitor
+	url = https://github.com/CrossPad/crosspad-serial-monitor.git
+[submodule "src/apps/crosspad-mixer"]
+	path = src/apps/crosspad-mixer
+	url = https://github.com/CrossPad/crosspad-mixer.git

.vscode/settings.json

@@ -0,0 +1,13 @@
+{
+  "VsCodeTaskButtons.showCounter": false,
+  "VsCodeTaskButtons.tasks": [
+    {
+      "label": "$(package) CP Tools",
+      "task": "CrossPad: App Manager"
+    },
+    {
+      "label": "$(zap) Run",
+      "task": "CrossPad: Run"
+    }
+  ]
+}

.vscode/tasks.json

@@ -0,0 +1,28 @@
+{
+  "version": "2.0.0",
+  "tasks": [
+    {
+      "label": "CrossPad: App Manager",
+      "type": "shell",
+      "command": "python3",
+      "args": ["${workspaceFolder}/scripts/app_manager.py"],
+      "presentation": {
+        "reveal": "always",
+        "panel": "dedicated",
+        "focus": true
+      },
+      "problemMatcher": []
+    },
+    {
+      "label": "CrossPad: Run",
+      "type": "shell",
+      "command": "${workspaceFolder}/scripts/run.sh",
+      "presentation": {
+        "reveal": "always",
+        "panel": "dedicated",
+        "focus": true
+      },
+      "problemMatcher": []
+    }
+  ]
+}

CLAUDE.md

@@ -4,7 +4,15 @@ This file provides guidance to Claude Code (claude.ai/code) when working with co
 
 ## Default Tools
 
-**Always prefer CrossPad MCP tools** (`crosspad_build`, `crosspad_run`, `crosspad_screenshot`, `crosspad_log`, `crosspad_test`, etc.) over manual bash commands for building, running, testing, and interacting with the simulator. The MCP server handles MSVC environment setup, paths, and simulator communication automatically.
+**Always prefer CrossPad MCP tools** over manual bash commands for building, running, testing, and interacting with the simulator. The MCP server handles MSVC/GCC environment setup, paths, and simulator communication automatically.
+
+Key tools:
+- `crosspad_build` — build/run/check simulator (`action: pc/pc_run/pc_check/pc_log`) and ESP-IDF firmware (`action: idf`)
+- `crosspad_test` — run Catch2 tests (`action: run/scaffold`)
+- `crosspad_sim` — screenshots, input, stats, settings (`action: screenshot/input/stats/settings_get/settings_set`)
+- `crosspad_repo` — git status and submodule diffs (`action: status/diff`)
+- `crosspad_code` — search symbols, query interfaces, list apps, scaffold (`action: search/interfaces/apps/scaffold`)
+- `crosspad_apps` — app package manager (`action: list/install/remove/update/sync`)
 
 ## Project Overview
 
@@ -85,16 +93,47 @@ src/
     PcApp.cpp                   — lightweight App class for launcher (no sequencer/CLI)
     pc_platform.h               — public API: pc_platform_init(), set_midi/audio/synth
 lib/ml_synth/                   — vendored ML_SynthTools FM synth engine
+lib/crosspad-core/              — submodule: portable C++ library
+lib/crosspad-gui/               — submodule: shared LVGL UI components
+scripts/
+  app_manager.py                — Python app manager (wrapper for crosspad-apps core)
+  run.sh                        — Smart build+run script
 tools/mcp-server/               — MCP development server (TypeScript, 16 tools)
 ```
 
 ### Submodules
 
+**Shared libraries** (in `lib/`):
+
 - **crosspad-core**: Portable C++ library — AppRegistry, IEventBus, PadManager, PadLedController, CrosspadSettings (IKeyValueStore), Stm32MessageHandler, platform interfaces (IClock, IMidiOutput, ILedStrip, IAudioOutput, ISynthEngine). Originally an ESP-IDF component; sources are listed manually in CMakeLists.txt.
 - **crosspad-gui**: LVGL UI components — theme, styles, launcher, status bar, widgets (keypad buttons, spinbox, radial menu, VU meter, file explorer, DFU panel, modals/toasts). Originally an ESP-IDF component; sources listed manually.
 - **lvgl**: LVGL v9.x graphics library
 - **FreeRTOS**: FreeRTOS Kernel (MSVC-MingW port on Windows, GCC POSIX on Linux/Mac)
 
+**Installable apps** (in `src/apps/crosspad-*/`, managed by app manager):
+
+- **crosspad-appstore**: Built-in App Store (cannot be removed)
+- **crosspad-mixer**, **crosspad-piano**, **crosspad-instructions**, **crosspad-serial-monitor**: Installable via `python3 scripts/app_manager.py install <name>` or via the App Store UI
+
+### App Management
+
+Apps are installed as git submodules in `src/apps/crosspad-*/`. CMake auto-discovers them via `file(GLOB)`. The app manager (`scripts/app_manager.py`) wraps the shared [crosspad-apps](https://github.com/CrossPad/crosspad-apps) core.
+
+**CLI commands:**
+
+```bash
+python3 scripts/app_manager.py list              # List available apps
+python3 scripts/app_manager.py install mixer     # Install an app
+python3 scripts/app_manager.py remove mixer      # Remove an app
+python3 scripts/app_manager.py update --all      # Update all installed apps
+python3 scripts/app_manager.py sync              # Sync manifest with disk
+python3 scripts/app_manager.py                   # Launch interactive TUI
+```
+
+**After install/remove:** `cmake -B build -G Ninja && cmake --build build` (CMake reconfigure picks up new sources).
+
+**Creating a new app:** See the [crosspad-appstore README](https://github.com/CrossPad/crosspad-appstore#creating-a-crosspad-app) for the app repo structure, `crosspad-app.json` format, and registration pattern.
+
 ### Platform Abstraction Pattern
 
 crosspad-core defines portable interfaces; this repo provides PC implementations: