Mcp Wuffs Streaming Json Parser

Added a Wuffs-backed streaming JSON parser for AI protocol parsing (MCP, A2A, OpenAI, Anthropic, etc.) with the following properties: incremental chunk-by-chunk parsing that resumes across arbitrary HTTP body chunk boundaries without buffering the full body; token-based processing with no DOM allocation — heap usage is proportional only to fields the handler opts into capturing, not to the total body size; AI-native field extraction that inlines scalar fields (e.g. model, method, id, params.name) into small bounded strings and captures large fields (e.g. messages[], params.arguments) as zero-copy byte-range references into the original body; and duplicate-key detection that rejects key-smuggling attacks (e.g. multiple "model" fields) with early mid-stream termination before the full body is consumed.