feat: add CI/CD workflow for automated builds and releases

[agarwalvishal]

🚀 Overview

Adds a comprehensive CI/CD workflow that automatically builds Claudia for Linux and macOS platforms and creates GitHub releases with downloadable installers.

📋 What This Adds

• Multi-platform builds: Linux (Ubuntu) and macOS (Apple Silicon)
• Automated releases: Creates GitHub releases when code is pushed to main
• Installer packages: .deb, .AppImage (Linux) and .dmg (macOS)
• Build optimization: Rust and Bun dependency caching
• Manual testing: workflow_dispatch support for manual runs
• Error handling: Build log uploads on failure

🔄 Relationship to Existing Workflows

This workflow complements the existing build-test.yml:

• build-test.yml: Fast CI testing with --no-bundle (existing)
• build.yml: Production builds with full installers (new)

Both serve different purposes and work together seamlessly.

🏗️ Technical Implementation

• Aligned dependencies: Uses identical system dependencies as build-test.yml
• Caching strategy: Implements Rust and Bun caching for faster builds
• Artifact management: 30-day retention with organized naming
• Semantic versioning: Uses version from Cargo.toml
• Security: Proper permissions and conditional release logic

🔧 Platform Support

• ✅ Linux: Fully supported (.deb, .AppImage)
• ✅ macOS: Apple Silicon only (.dmg)
• ❌ Windows: Ready but commented out (pending Windows build fails: Invalid icon.ico format and Unix-only imports #83 fixes)
• ❌ macOS Universal: Ready but commented out (pending Intel binary)

📦 Release Process

• Automatic: Triggers on pushes to main branch
• Manual: Can be triggered via workflow_dispatch for testing
• Versioning: v{cargo-version}-build{run-number} format
• Artifacts: All installers attached to GitHub releases

🔍 Testing

• Builds successfully on Linux and macOS
• Creates proper installer packages
• Uploads to GitHub releases correctly
• Caching works for faster subsequent builds
• Manual workflow dispatch functions properly

🚧 Known Limitations

• Windows builds disabled: Due to #83 (icon format + Unix imports)
• macOS Universal disabled: Missing Intel Claude Code binary
• Lockfile flag removed: Due to upstream dependency changes (bun.lockb conflicts)

🔮 Future Compatibility

Workflow is designed to automatically support additional platforms:

• Windows: Uncomment section after Windows build fails: Invalid icon.ico format and Unix-only imports #83 is resolved
• macOS Universal: Uncomment section after Intel binary is added

🎯 Benefits

• User Experience: Automated, reliable downloads for end users
• Maintainer Experience: Reduces manual release overhead
• Quality Assurance: Consistent builds across platforms
• Scalability: Ready for future platform expansion

📚 Related Issues

• Addresses need for automated release distribution
• Complements Windows Support for Claudia - Community Fix Available 4.2 FINAL #78 (Windows support when ready)
• Works around Windows build fails: Invalid icon.ico format and Unix-only imports #83 (Windows build issues)

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Ready for review ✅ Production tested ✅ Future-proof ✅