[Phase 1a] Extend MCP schema with promptBehavior metadata

[usepowershell]

Part of #98

Update the MCP tool schema to advertise which commands may prompt for input.

Subtasks

• Add PromptBehaviorMetadata class to schema
• Add fields: mayPrompt, supportedPromptTypes, timeoutSeconds, note
• Update McpToolFactoryV2 to populate promptBehavior
• Update schema generation to detect prompt-triggering commands
• Update MCP response format to include promptBehavior
• Client-facing docs for retry workflow
• Tests

Effort: 3-5 days