Clean up abort signal listeners

[fallintoplace]

Summary

• keep caller-provided abort signals connected after response headers arrive
• remove the abort listener after SDK-owned body consumption finishes or is cancelled
• add regression coverage for normal body parsing, aborting during a pending body read, and streamed response iteration

Why

fetchWithTimeout() previously cleaned up the abort listener as soon as fetch() resolved. That avoided the listener leak, but it also disconnected caller aborts while APIPromise was still parsing the response body or while a stream was being consumed.

This keeps the listener attached through body consumption, then removes it from the parse and stream finalization paths.

Tests

• ./node_modules/.bin/jest tests/index.test.ts --runInBand
• ./node_modules/.bin/prettier --check src/client.ts src/internal/parse.ts src/core/streaming.ts tests/index.test.ts
• ./node_modules/.bin/eslint src/client.ts src/internal/parse.ts src/core/streaming.ts tests/index.test.ts
• ./node_modules/typescript/bin/tsc
• ./scripts/build

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[chatgpt-codex-connector]

Keep abort signal attached until the body is consumed

This finally runs as soon as fetch resolves with response headers, but APIPromise parses the body later in defaultParseResponse and streaming responses are consumed even later. If a caller aborts their request signal after headers arrive (for example while waiting on a slow JSON body or while iterating a streamed response), this listener has already been removed, so the internal controller passed to fetch is never aborted and the body read/stream continues instead of cancelling.

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