Add hand-rolled JSON-RPC 2.0 implementation for MCP server transports.
Module: crates/pdftract-cli/src/mcp/framing/
- Id enum with Number/String/Null variants preserving JSON type
- Request, Response, Notification, ErrorObject structs
- BatchMessage for batch request handling
- Strict jsonrpc version validation (must be "2.0")
- All 6 spec-defined error codes (-32700, -32600, -32601, -32602, -32603, -32099..-32000)
- Constructor helpers for common patterns
Acceptance criteria verified:
- Round-trip serialization/deserialization
- ID type preservation (number/string/null)
- Parse error responses with null id
- Method not found error construction
- Notification detection (no id field)
- Batch request handling
- Rejection of invalid jsonrpc versions
- Empty batch rejection
16 unit tests covering all spec requirements.
Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>
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