Add: Debug logging for MCP skill startup time

[FL4TLiN3]

Summary

• Add skillStarting event emitted when MCP skill initialization begins
• Add skillStderr event to capture child process stderr output
• Add connectDurationMs and totalDurationMs fields to skillConnected event

Background

initializeRuntime to skillConnected takes approximately 7 seconds. These structured events help identify the bottleneck (binary startup time vs MCP handshake time).

New Events

skillStarting

{
  skillName: string
  command: string
  args: string[]
}

skillStderr

{
  skillName: string
  message: string
}

skillConnected (updated)

{
  skillName: string
  serverInfo?: { name: string; version: string }
  connectDurationMs?: number  // NEW
  totalDurationMs?: number    // NEW
}

Test plan

• TypeScript compiles without errors
• All unit tests pass
• Biome lint passes

Closes #49

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1 Skipped Deployment

Project	Deployment	Preview	Comments	Updated (UTC)
perstack	Ignored	Preview		Dec 4, 2025 10:26pm

[codecov]

Codecov Report

❌ Patch coverage is 0% with 9 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
packages/runtime/src/skill-manager/mcp.ts	0.00%	9 Missing ⚠️

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[cursor]

Bug: Stderr listener attached before process starts, never receives data

The transport.stderr listener is attached at lines 79-82, but the child process isn't spawned until connect() is called at line 85. The StdioClientTransport.stderr property returns the spawned process's stderr stream, which is only available after start() (called internally by connect()). Since transport.stderr is null or undefined before the process starts, the if (transport.stderr) check fails silently, and the stderr listener is never attached. This defeats the main purpose of this PR - stderr output from the MCP skill will never be logged.