Harden non-streaming fallback tests for fetchWithCorsProxy

[ashfame]

Summary

Follow-up to #3440, specifically addressing Brandon's comments the request to assert unsupported streaming in each fallback test and the concern that resetting the cache allows Node.js/V8 to detect streaming support.

• The non-streaming fallback suite now sets the cached supportsReadableStreamBody() result to false in beforeEach() and asserts that value before every test runs.
• The suite resets that test-only cache in afterEach(), keeping the test state hermetic.
• The proxy-retry test now correctly expects only direct-fetch and proxy-fetch calls, because no detection probe runs when unsupported mode is already cached.

Test plan

• npm exec nx test php-wasm-web-service-worker --testFile=fetch-with-cors-proxy.spec.ts
• npm exec nx lint php-wasm-web-service-worker

[Copilot]

Pull request overview

Note

Copilot was unable to run its full agentic suite in this review.

Strengthens the “non-streaming fallback” test suite for fetchWithCorsProxy by deterministically forcing supportsReadableStreamBody() to report “unsupported”, ensuring tests actually exercise the intended fallback path.

Changes:

• Added a __testing.setStreamBodySupported(false) hook to force non-streaming mode in tests.
• Updated the non-streaming fallback test setup to assert the forced mode and simplified fetch mock ordering/call counts accordingly.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
packages/php-wasm/web-service-worker/src/utils.ts	Adds a test-only setter to control the cached supportsReadableStreamBody() result.
packages/php-wasm/web-service-worker/src/fetch-with-cors-proxy.spec.ts	Forces non-streaming mode in beforeEach and updates mocks/assertions to match the new deterministic behavior.

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[brandonpayton]

@ashfame Thanks for faithfully following up on prior PR review comments. Let's merge this!