fix(node): forward response Set-Cookie fields separately

[rudycelekli]

Preserve separate Set-Cookie header values when adapting a web Response to Node. The adapter forwards getSetCookie() as a string array instead of losing earlier cookies during header iteration.

Validation: official package typecheck, ESLint and Prettier passed. 15 adapter tests passed with explicit source aliases for core-internal and server/_shims, matching tsconfig paths. Default Vitest collection remains blocked by private workspace exports pointing to unbuilt dist; core/server builds did not resolve that setup issue.

The cookie regression fails on unchanged source and passes after the fix. No default-runner, full SDK monorepo, or hosted CI pass is claimed. AI-assisted implementation and tests, independently reviewed before publishing this draft.

[changeset-bot]

🦋 Changeset detected

Latest commit: 5bb975d

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@modelcontextprotocol/node	Patch

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commit: 5bb975d

[karaaslanz]

Independent bounded verification of exact PR head 5bb975d6faf3aa08d86d56c8ef0946b7fb8ce9a6 (Node 22, real node:http response). I ran the changed header-forwarding block against a web Response with two separate Set-Cookie values. Baseline header iteration without getSetCookie() forwarded only the last cookie; the PR's getSetCookie() override passed both distinct values to a real Node HTTP client. Additional cases with a single cookie and no cookies, each including an unrelated header, also passed (3/3). This confirms the targeted adapter behavior and doesn't represent a full repo/test suite run or a claim about every supported runtime. No blocking issue found in the cookie-forwarding path tested.