(docs) add CLAUDE.md project instructions

CLAUDE.md

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+# UVCCamera
+
+> USB Video Class (UVC) camera library for Android + Flutter plugin
+
+## Project Context
+
+| Attribute | Value |
+|-----------|-------|
+| **License** | Apache-2.0 |
+| **Min SDK** | 21 (Android 5.0) |
+| **Compile SDK** | 34 (Android 14) |
+| **Java Compatibility** | 11 (build requires JDK 17) |
+| **Target ABIs** | armeabi-v7a, arm64-v8a |
+| **Gradle** | 8.13, Kotlin DSL, version catalog |
+| **Flutter** | >=3.29.2, Dart SDK >=3.7.0 |
+| **Distribution** | Maven Central (`org.uvccamera:lib`), pub.dev (`uvccamera`), GitHub Packages |
+
+## Structure
+
+| Path | Purpose |
+|------|---------|
+| `lib/` | Android library module (`org.uvccamera.lib`) |
+| `lib/src/main/java/` | Java API (UVCCamera, USBMonitor, DeviceFilter) |
+| `lib/src/main/jni/` | Native C/C++ (libuvc, libusb, libjpeg, UVCCamera JNI) |
+| `flutter/` | Flutter plugin (`uvccamera`) |
+| `flutter/lib/` | Dart API |
+| `flutter/android/` | Flutter Android platform implementation (Java) |
+| `flutter/example/` | Flutter example app |
+| `usbCameraCommon/` | Shared Android UI utilities for test apps |
+| `usbCameraTest*/` | Android test/demo applications |
+| `upstreams/` | Git submodules referencing upstream forks |
+| `gh-pages/` | GitHub Pages build assets |
+| `gradle/libs.versions.toml` | Dependency version catalog |
+
+## Conventions
+
+### Commits
+
+Format: `(type) scope: description`
+
+| Type | Meaning |
+|------|---------|
+| `fix` | Bug fix |
+| `imp` | Improvement/enhancement |
+| `chore` | Maintenance (deps, CI, tooling) |
+| `docs` | Documentation |
+
+Scope prefix when targeting a specific module: `flutter:`, `ci:`, `lib:`
+
+Cherry-picked commits use trailers:
+```
+Cherry-picked-from: source/repo@sha (or source/repo#PR)
+Co-authored-by: Original Author <email>
+```
+
+### Branches
+
+| Type | Pattern | Example |
+|------|---------|---------|
+| Feature | `feat/description` | `feat/flutter/pause-resume-preview` |
+| Fix | `fix/description` | `fix/preview-size-comparison` |
+| Cherry-pick | `cherry-pick/source-description` | `cherry-pick/hthetiot-fix-rotation` |
+
+### Naming
+
+- Java packages: `com.serenegiant.usb` / `com.serenegiant.utils` (legacy upstream)
+- Library namespace: `org.uvccamera.lib`
+- Flutter plugin package: `org.uvccamera.flutter`
+- Dart files: `uvccamera_*.dart` (snake_case with prefix)
+- Gradle modules: camelCase (`usbCameraTest`, `usbCameraCommon`)
+
+### Code Style
+
+Per `.editorconfig`: 4-space indent, 120 char max, LF line endings, UTF-8. YAML uses 2-space indent.
+
+## Development
+
+### Build Android library
+
+```shell
+./gradlew :lib:assembleRelease
+```
+
+### Publish to local Maven (required before Flutter build)
+
+```shell
+./gradlew :lib:publishToMavenLocal
+```
+
+### Build Flutter example
+
+```shell
+cd flutter/example
+flutter build apk
+```
+
+### Run full build chain
+
+```shell
+./gradlew assembleRelease publishToMavenLocal && cd flutter/example && flutter build apk
+```
+
+## Release
+
+Tag-triggered: push a semantic version tag to trigger the release workflow.
+
+```shell
+git tag X.Y.Z
+git push origin X.Y.Z
+```
+
+The CI workflow automatically publishes to Maven Central, pub.dev, and GitHub Packages.
+
+## CI
+
+| Workflow | Trigger | Purpose |
+|----------|---------|---------|
+| `ci.yaml` | Push to main, PRs to main | Build lib, publish snapshots, build GitHub Pages |
+| `release.yaml` | Version tag push | Full release: build, sign, publish all artifacts |
+
+Snapshot versions: `main-SNAPSHOT` (main branch), `PR-{N}-SNAPSHOT` (pull requests).
+
+## Native Layer
+
+The native code uses ndk-build (not CMake). Entry point: `lib/src/main/jni/Android.mk`.
+
+Key native libraries:
+- **libuvc** — USB Video Class protocol implementation
+- **libusb** — USB device access
+- **libjpeg** — JPEG encoding/decoding
+- **UVCCamera** — JNI bridge and pipeline system
+
+The pipeline architecture (`lib/src/main/jni/UVCCamera/pipeline/`) handles frame processing with buffered, preview, capture, and callback pipelines.
+
+## Fork Context
+
+Hard fork of `saki4510t/UVCCamera`. Upstream submodules in `upstreams/` for reference. Community improvements are cherry-picked with attribution trailers.