fix(mint): avoid crashes on HTTP/2 request resets

[yordis]

• closes Mint Adapter is failing to handle the :server_closed_request error reason #553 by anchoring the change to the live HTTP/2 request-reset behavior that originally crashed the Mint adapter
• preserve Mint's request-scoped error for callers instead of turning that response into a FunctionClauseError inside the adapter
• keep the regression proof at the transport level so future changes stay pinned to the reported failure mode

[cursor]

PR Summary

Medium Risk
Changes error handling in the core Mint adapter receive/reduce path and stream body enumeration, which can affect how callers observe failures and connection lifecycles under HTTP/2 resets.

Overview
Prevents the Mint adapter from crashing when Mint emits request-scoped HTTP/2 errors (e.g., server resets) by making reduce_responses/3 propagate {:error, error} from {:error, ref, error} responses and by raising those errors during body_as: :stream enumeration.

Adds end-to-end regression coverage using a real TLS Cowboy HTTP/2 server that triggers internal errors and mid-stream resets, asserting both Mint’s emitted responses and Tesla’s adapter behavior; also extends push promise coverage to validate pushed-stream responses from a live HTTP/2 server.

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[Copilot]

Pull request overview

This PR addresses Tesla’s Mint adapter crash reported in issue #553 by ensuring Mint HTTP/2 stream reset errors (e.g. {:server_closed_request, :internal_error}) are surfaced to callers instead of causing a FunctionClauseError.

Changes:

• Introduces Tesla.Adapter.Mint.ResponseAccumulator to reduce Mint responses while halting on request-scoped {:error, ref, error} tuples.
• Updates the adapter receive path to use the new accumulator and return the Mint error tuple.
• Adds regression tests, including a live Cowboy HTTP/2 reproduction that triggers an INTERNAL_ERROR stream reset.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
lib/tesla/adapter/mint.ex	Adds a response accumulator and integrates it into the Mint adapter receive loop to avoid crashes on request reset errors.
test/tesla/adapter/mint_test.exs	Adds unit coverage for the accumulator plus an end-to-end HTTP/2 stream reset reproduction/regression test.
test/support/mint_internal_error_handlers.ex	Adds Cowboy request/stream handlers used to reproduce the HTTP/2 reset scenario in tests.

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[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.

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