Add CLAUDE.md (#177)

Author: Kyle-Ye

CLAUDE.md

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+# OpenAttributeGraph Project Guide
+
+## Project Overview
+OpenAttributeGraph is a Swift package that provides attribute graph functionality, serving as a foundation for OpenSwiftUI project. It interfaces with DarwinPrivateFrameworks for compatibility testing.
+
+## Development Workflow
+
+### 1. Make Changes and Commit
+- Implement your feature or fix
+- Test locally
+- Commit changes with descriptive messages
+
+### 2. (Optional) Compatibility Testing
+If changes affect the interface with DarwinPrivateFrameworks:
+```bash
+# Generate AG template
+Scripts/gen_ag_template.sh
+`
+# Update code in ../DarwinPrivateFramework from .ag_template
+
+# Set useLocalDeps to true in Package.swift
+xed -l -c 's/let useLocalDeps = envEnable("OPENATTRIBUTEGRAPH_USE_LOCAL_DEPS")/let useLocalDeps = true/' Package.swift
+
+# Build and test with both compatibility modes:
+OPENATTRIBUTEGRAPH_COMPATIBILITY_TEST=0 swift build
+OPENATTRIBUTEGRAPH_COMPATIBILITY_TEST=1 swift build
+```
+
+### 3. Create DarwinPrivateFramework PR
+After testing, discard local changes from step 2:
+```bash
+# Discard any local testing changes
+git checkout -- Package.swift
+
+# Create PR for DarwinPrivateFramework
+Scripts/bump_ag_pr.sh <branch-name>
+```
+
+### 4. Update Dependencies
+After the DarwinPrivateFramework PR is merged:
+```bash
+# Update package dependencies
+swift package update DarwinPrivateFramework
+
+# Commit the updated Package.resolved
+git add Package.resolved
+git commit -m "Update DarwinPrivateFrameworks dependency"
+```
+
+### 5. Create Project PR
+```bash
+# Create PR for the current branch
+gh pr create --base main --head <current-branch>
+```
+
+## Key Scripts
+- `Scripts/gen_ag_template.sh` - Generates AG template for compatibility testing
+- `Scripts/bump_ag_pr.sh` - Creates PR for DarwinPrivateFramework updates
+
+## Environment Variables
+- `OPENATTRIBUTEGRAPH_COMPATIBILITY_TEST=0` - Test without compatibility mode
+- `OPENATTRIBUTEGRAPH_COMPATIBILITY_TEST=1` - Test with compatibility mode
+
+## Important Notes
+- Always test compatibility when changing interfaces
+- Ensure DarwinPrivateFramework PR is merged before creating main project PR
+- Keep Package.resolved updated after dependency changes