* fix: preserve whitespace-only chunks in SSE stream
Fixes issue #138 where Claude models would swallow spaces between words because whitespace-only chunks (e.g., " ") were being filtered out as empty.
Changes:
- Modified sse-streamer.js to only skip truly empty strings (""), preserving strings that contain only whitespace.
- Added regression test case in tests/test-streaming-whitespace.cjs to verify whitespace preservation.
* test: add streaming whitespace regression test to main suite
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Co-authored-by: walczak <walczak@ial.ruhr>
