[SPEC-6] Integrate Zed Editor with SpecSafe

[LaloLalo1999]

Add SpecSafe integration for Zed editor. Zed uses Agent Client Protocol (ACP) and Model Context Protocol (MCP) for AI extensibility. Create SpecSafe plugin/agent for Zed Agent Panel. Support inline transformations and agentic editing with spec validation. \n\nLinear: SPEC-6