fix(x402): do not silently flip HTTP method on 404

[SashaMIT]

Summary

make_http_request retried a 404 with the HTTP method flipped (GET becomes POST, POST becomes GET) and the caller's body attached. On services that map both methods to one path (common in REST APIs, e.g. GET /items/123 vs POST /items), that silently converts an intended read into a write the agent never chose to make. For an agent framework, silent method mutation is an integrity hazard: the model asked for a read, the tool executed a write.

Fix

Return the 404 with a hint naming the method tried, so switching methods becomes an explicit agent decision:

The service returned 404 for GET. If it expects a different method, call this action again with that method explicitly.

Test plan

• New regression test: 404 on GET produces exactly one request, method unchanged, hint returned
• Full x402 suite passes (22/22); tsc --noEmit, eslint, prettier clean

Made with Cursor

[cb-heimdall]

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