- Add mapMCPContentBlocks() helper mapping SDK ContentBlock[] to MCPContentBlock[]
- Extract tool.outputSchema via FromSchema() when present, fall back to Type.Unknown()
- Handler returns mcpEnvelope() with structured/legacy data path
- structuredContent preferred as data when present, Value.Cast() when outputSchema is known
- isError: true wrapped in envelope meta, NOT thrown
- Transport-level config errors throw CallError
- Unknown MCP content block types fall back to { type: 'text', text: JSON.stringify(block) }
- Add 20 tests for mapMCPContentBlocks and envelope detection
