Claude Agent SDK Integration

What: Added support for tracking when Claude Code is invoked through the Claude Agent SDK, enabling better analytics and contextual identity.

How it works: When the CLAUDE_AGENT_SDK_VERSION environment variable is set, it's automatically included in telemetry and user agent strings.

Details:

• User agent string enhanced from claude-cli/1.0.128 (external, <entrypoint>) to claude-cli/1.0.128 (external, <entrypoint>, agent-sdk/<version>) when SDK is used
• New agentSdkVersion field in telemetry data (line 440142)
• Enables Anthropic to distinguish direct CLI usage from SDK-mediated usage
• Evidence: IM() user agent function at line 368228, telemetry field at lines 140142-440144