Add TypeScript Spector coverage for multipart and optional response bodies

[Copilot]

Adds TypeScript integration coverage for 19 supported Spector scenarios. Unsupported SSE protocol handling and XML continuation remain excluded with concise blockers.

Spector test results

Streaming_Sse_Protocol_Data

• ❌ Failed: withEnvelope — generated clients expose raw streams without typed SSE event parsing.
• ❌ Failed: withoutEnvelope — generated clients expose raw streams without typed SSE event parsing.

Streaming_Sse_Protocol

• ❌ Failed: id — SSE ID metadata is not parsed.
• ❌ Failed: invalidId — SSE ID validation is not implemented.
• ❌ Failed: invalidRetry — SSE retry metadata is not parsed.
• ❌ Failed: reconnect — reconnection and Last-Event-ID handling are not implemented.
• ❌ Failed: retry — SSE retry metadata is not parsed.

Response_BodyOrNoContent — response-body-or-no-content.test.ts

• ✅ Added: getBody
• ✅ Added: getNoContent

Payload_Pageable_XmlPagination — payload-pageable.test.ts

• ❌ Failed: listWithContinuation — iteration stops after the first XML page without sending the continuation marker.

Payload_MultiPart_FormData — payload-multipart.test.ts

• ✅ Added: anonymousModel
• ✅ Added: basic
• ✅ Added: binaryArrayParts
• ✅ Added: checkFileNameAndContentType
• ✅ Added: fileArrayAndBasic
• ✅ Added: jsonPart
• ✅ Added: multiBinaryParts
• ✅ Added: optionalParts
• ✅ Added: withWireName

Payload_MultiPart_FormData_HttpParts_ContentType — payload-multipart.test.ts

• ✅ Added: imageJpegContentType
• ✅ Added: optionalContentType
• ✅ Added: requiredContentType

Payload_MultiPart_FormData_HttpParts — payload-multipart.test.ts

• ✅ Added: jsonArrayAndFileArray

Payload_MultiPart_FormData_HttpParts_NonString — payload-multipart.test.ts

• ✅ Added: float

Payload_MultiPart_FormData_File — payload-multipart.test.ts

• ✅ Added: uploadFileArray
• ✅ Added: uploadFileRequiredFilename
• ✅ Added: uploadFileSpecificContentType

• Fixes [Copilot] Verify and implement Spector tests for 9 scenario groups #5408

[azure-pipelines]

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[pkg-pr-new]

Open in StackBlitz

npm i https://pkg.pr.new/@azure-tools/typespec-ts@5411

commit: 686b3c4

[azure-sdk-automation]

You can try these changes here

🛝 Playground	🌐 Website

[Jialin Huang (JialinHuang803)]

LGTM.

[Qiaoqiao Zhang (qiaozha)]

please check whether those MFD related issues are resolved and could be closed?

[Jialin Huang (JialinHuang803)]

please check whether those MFD related issues are resolved and could be closed?

The items listed in the #4757 are not covered by these spector tests. Let's keep the issue open.