fix: support CR line endings in SSE

[KennyMcSimpson]

Summary

parseSSE splits only on LF. With bare CR line endings, two events such as data: first\r\rdata: second\r\r become one malformed data value instead of two events. SSE permits CR, LF and CRLF as line endings.

Handle all three forms, including CRLF split across network chunks. A CR completes the line immediately, so a finished event is delivered while the stream remains open. Existing field parsing and final-event flushing are preserved.

Tests

• Add coverage at every byte boundary for CR, LF and CRLF, including empty chunks and fragmented UTF-8.
• Check mixed endings with byte-by-byte delivery and dispatch before EOF.
• bun test — 597 passed; bun test test/client/stream.test.ts — 19 passed.
• bun run typecheck, bun run lint and bun run build pass. Lint reports one existing warning in test/sdk/speech.test.ts.
• The CI compile/version smoke check and git diff --check pass.

Tested with Bun 1.4.2. Three new regression tests fail before the fix.

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