Add ClaudeCliProvider that executes the local CLI as a subprocess,
enabling PicoClaw to leverage advanced capabilities (MCP tools,
workspace awareness, session management) through any messaging channel.
- Implement LLMProvider interface via subprocess execution
- Support --system-prompt, --model, --output-format json flags
- Parse real v2.x JSON response format including usage tokens
- Handle error responses, stderr, context cancellation
- Register "claude-cli", "claude-code", "claudecode" aliases in CreateProvider
- 56 unit tests with mock scripts + 3 integration tests against real binary
- 100% coverage on all functions except stripToolCallsJSON (85.7%)
