readline.createInterface runs an expensive Unicode line-break regex + extra
stream/string-decoder machinery per chunk. The main transcript parser (parseJsonlStream)
already uses a buffer + manual newline split; these per-team readers still used readline.
Add readJsonlLines(): an async generator that yields a JSONL file's lines via a chunked
utf8 stream read + a plain '\n' split (drop-in for 'for await (const line of rl)'), so the
consumers' loop bodies are unchanged. Stream is utf8-decoded before splitting, so multi-byte
chars across chunk boundaries are safe; trailing CR (CRLF) is stripped; empty lines and a
final newline-less line are yielded, matching readline; breaking out of the loop destroys
the stream via the generator's finally.
Adopt it in MemberStatsComputer, TaskBoundaryParser, and FileContentResolver (file-history
scan). Behavior-identical (their existing tests pass: 18 + 6 + 12) plus 6 new tests for the
generator (CRLF, empty lines, no-trailing-newline, early break, multi-byte chunk boundary).
Note: session-browser readline paths (jsonl metadata extractor, metadataExtraction,
SessionContentFilter) are off the launch path and left as-is for now.
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