[Bug]: SSE clients silently drop events with standalone CR line endings

## What happened

JSON-RPC and HTTP+JSON clients silently yield no updates when a valid SSE response uses standalone CR (`\r`) line endings. The same event works with LF (`\n`) or CRLF (`\r\n`). A finite response completes without an error or an event.

## What I expected

All three SSE line endings should deliver the same task update, including when line delimiters cross network chunk boundaries.

## Steps to reproduce

1. Create a `RestTransport` with a mock fetch returning HTTP 200 and `Content-Type: text/event-stream`.
2. Use this response body (JavaScript string literal):

```js
'data: {"task":{"id":"task-1","contextId":"ctx-1","status":{"state":"TASK_STATE_WORKING"}}}\r\r'
```

3. Iterate `resubscribeTask({ id: 'task-1', tenant: '' })` until completion. It yields **0** events.
4. Replace `\r\r` with `\n\n` or `\r\n\r\n`. Both yield **1** event.
5. Repeat with `JsonRpcTransport`, wrapping the task payload in `{ jsonrpc: '2.0', id: , result: }`. The results are identical.

## Additional context

Reproduced with the response split into one-byte chunks; the relevant client/parser code matches upstream main `ae20aca7d6fbc94c839a37d945ec637642289227`.

The HTML SSE standard explicitly allows CRLF, LF, and standalone CR as line endings:
https://html.spec.whatwg.org/multipage/server-sent-events.html#parsing-an-event-stream

This can silently discard task updates from a conforming remote agent. Please cover standalone CR as well as split CRLF delimiters, so adding CR support does not introduce duplicate event boundaries.

Sieh dir die SSE-Parsing-Logik im Client-/Transport-Code an, wahrscheinlich in `RestTransport` und `JsonRpcTransport`. Der Testfall ist vorhanden; richte zunächst den Mock-Fetch mit dem angegebenen Response-Body ein. Führe die vorhandenen Tests aus, um den Fehler zu sehen, und passe dann den Parser so an, dass er eigenständige CR-Zeilenenden gemäß der HTML-Spezifikation verarbeitet. Stelle sicher, dass der Fix auch geteilte Trennzeichen über Chunk-Grenzen hinweg verarbeitet.

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