fix(core): avoid extending TransformStream in EventStreamDecoderStream

[dinwwwh]

EventStreamDecoderStream no longer extends TransformStream. Extending resolves the global at module-evaluation time, so merely importing @standardserver/core crashed on runtimes that don't provide TransformStream — even when the stream class was never used. The class now composes a TransformStream created in its constructor and exposes its readable/writable pair, so the global is only needed when an instance is actually constructed.

Fixes

• Importing @standardserver/core works on runtimes without a global TransformStream; only constructing EventStreamDecoderStream requires it.
• .pipeThrough(new EventStreamDecoderStream()) behaves exactly as before — the class satisfies ReadableWritablePair<EventStreamMessage, string>. The only observable difference is that instances are no longer instanceof TransformStream (nothing in the repo relied on that).

Testing

• New test stubs out the global TransformStream and asserts a fresh import of the module still succeeds; verified it fails against the previous extends implementation.
• Full workspace suite passes (59 files, 1075 tests) and tsc --noEmit is clean for core and fetch.

[pkg-pr-new]

• @standardserver/hono-node-playground
• @standardserver/node-http-playground

@standardserver/aws-lambda

npm i https://pkg.pr.new/@standardserver/aws-lambda@78

@standardserver/core

npm i https://pkg.pr.new/@standardserver/core@78

@standardserver/fastify

npm i https://pkg.pr.new/@standardserver/fastify@78

@standardserver/fetch

npm i https://pkg.pr.new/@standardserver/fetch@78

@standardserver/node

npm i https://pkg.pr.new/@standardserver/node@78

@standardserver/peer

npm i https://pkg.pr.new/@standardserver/peer@78

@standardserver/shared

npm i https://pkg.pr.new/@standardserver/shared@78

commit: 622f100

[pullfrog]

✅ No new issues found.

Reviewed changes

• EventStreamDecoderStream now implements ReadableWritablePair<EventStreamMessage, string> instead of extends TransformStream, composing a TransformStream in the constructor and exposing its readable/writable pair — deferring the global-after-reference until an instance is constructed.
• New regression test stubs TransformStream to undefined and re-imports ./decoder, verifying module import no longer crashe- resolving the global at import time.

The refactor is sound: ReadableStream/WritableStream are type annotations (type-erased at compile time), so the only runtime global use is the new TransformStream(...) inside the constructor. grep confirms every caller is .pipeThrough(new EventStreamDecoderStream()) (core tests, package/fetch/src/event-stream.ts:9, README), which only needs the ReadableWritablePair shape — nothing relies on instanceof TransformStream. The new test is meaningful (the old extends impl throws on import when the global is undefined) and cleans up via onTestFinished.

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[codspeed-hq]

Merging this PR will not alter performance

✅ 26 untouched benchmarks
⏩ 108 skipped benchmarks¹

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_{Comparing claude/transformstream-no-extend-936eb2 (622f100) with main (cd7c12f)²}

Footnotes

1. 108 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on main (9dd3c23) during the generation of this report, so cd7c12f was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩