Ensure Newline After HTTP Body in debug_dev Output

[sliumdx]

🧩 Ensure Newline After HTTP Body in debug_dev Output

📌 Problem

When using HTTPClient#debug_dev with a shared output (e.g., writing to $stdout), the HTTP response body is written without a trailing newline. This leads to problems when the stream is reused for other log outputs

In some systems, this prevents proper JSON log parsing, causing logs to be dropped entirely.

✅ Solution

This PR ensures that a newline is always written after the HTTP response body when using debug_dev. This makes debug_dev safer to use with shared output streams like $stdout or a Tee stream, where multiple JSON logs may be written in sequence.

🔬 Tests

Two new tests are added to verify this behavior:
• test_debug_dev_shared_dev
• test_debug_dev_stream_shared_dev

These assert that any content appended to the shared debug_dev stream after a request appears on a new line, preventing log merging.

@nahi