Praxis mode 6/8: Port the MCP and A2A parsers #1724

Part of #1714 · phase A, delivery step 6 · Section 3 (The parsers) · design in #1717 (docs/superpowers/specs/2026-11-07-praxis-mode-design.md)

Goal

Finish the parser ports, each behind its own parity gate.

Scope

• cortex_parse for MCP: a port of core/parse/mcp.
• cortex_parse for A2A: a port of core/parse/a2a.
• Each one behind the parity gate from Praxis mode 1/8: Add the Rust workspace and port the inference parser #1718.

Done when

• Every MCP and A2A fixture from Turn the MCP, A2A and inference parsers into libraries, with saved real-traffic test cases #1503 gives the same event JSON in Go and in Rust.

Depends on

#1718.

Assisted-By: Claude (Anthropic AI) noreply@anthropic.com