feat(mcp): expand pods server operations and codify architecture

[victoriacheng15]

Summary

Expanded the mcp-pods server with active operational tools (logs and deletion) and updated the architectural documentation to codify domain-isolated service patterns. These changes move the platform from passive observation to active agentic remediation while enforcing strict lifecycle standards across all MCP signals.

List of Changes

• Operational Agency: Implemented get_pod_logs and delete_pod capabilities, enabling agents to perform real-time diagnosis and first-level remediation without human intervention.
• Architectural Codification: Updated ADR 018 to formalize the domain-isolated architecture, extending the pattern to include active operations and standardizing on signal-based lifecycle management for all MCP binaries.
• Systemic Robustness: Enhanced the shared MCP registry with type-safe handlers and comprehensive test coverage, ensuring reliable tool execution and error reporting as the agentic control plane scales.

Verification

• go test -v ./internal/mcp/providers/... (Verified log retrieval and deletion logic)
• go test -v ./internal/mcp/tools/... (Verified operational tool handlers)
• Verified mcp-pods ready message and registry integration