Complete implementation planning for CLI app with MFA

- Created implementation plan with technical context
- Developed data models for User Session, Sync Job, and Authentication Token
- Defined API contracts for authentication, sync triggering, and status checking
- Created quickstart guide for CLI usage
- Updated agent context with new technology stack
- Verified constitution compliance for all design decisions

specs/006-cli-auth-sync-mfa/research.md

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+# Research Findings for CLI App with MFA Support
+
+## Phase 0: Outline & Research
+
+### Decision
+Selected Click as the CLI framework for the Python application based on the project constitution's requirement for CLI interfaces (must be Click or Typer). Decided to create a new CLI module that interfaces with the existing API structure.
+
+### Rationale
+- The constitution specifically requires either Click or Typer for CLI interfaces
+- Click provides excellent support for multi-level commands which is needed for auth/sync/status operations
+- Click has good support for handling MFA flows through prompts
+- Consistent with the existing backend architecture of the project
+
+### Technology Choices Made
+- **CLI Framework**: Click (as required by constitution)
+- **API Client**: httpx (modern, async-capable, excellent for API interactions)
+- **Configuration**: YAML (as required by constitution)
+- **Output Formats**: JSON, table, CSV (as required by constitution)
+- **Token Storage**: Local JSON file with appropriate security measures
+- **Authentication Flow**: OAuth2/MFA integration with existing backend API
+
+### Alternatives Considered
+- **Typer vs Click**: Typer offers better type hints integration, but Click was selected to match constitution requirements
+- **argparse**: Simpler but lacks the advanced features needed for this CLI application
+- **Direct HTTP requests**: httpx was chosen over basic requests library for better async support and API interactions
+
+### Integration Approach
+The CLI app will integrate with the existing backend API, reusing authentication mechanisms and sync endpoints. This approach leverages existing functionality while providing a new interface for users who prefer command-line operations.
+
+### Security Considerations
+- Local token storage will use appropriate file permissions (600)
+- MFA handling will follow platform-appropriate secure input methods
+- Token refresh mechanisms will be implemented to handle expiration