feat(mcp): publish model authoring guidance

[jmgilman]

Summary

• publish concise authoring and recovery guidance in all three tools/list descriptions
• document the same discovery, execution, resource-limit, and policy-outcome workflow in the MCP reference
• assert durable description cues through the official in-memory MCP client

Verification

• mise exec -- go test ./mcpserver -run '^TestNewRegistersExactlyThreeTools$' -count=1
• raw stdio MCP handshake and tools/list against the branch-built server
• three fresh blind OMP JSON-mode agents: onboarding lookup, multi-capability composition, and three-error recovery all completed through the public MCP tools
• mise exec -- moon run root:check
• LSP diagnostics on mcpserver/*.go