fix: read-idle timeout on SSE so a stalled stream can't hang events()

[wei-hai]

Found running a real >10-minute job against prod: the SSE stream went silent at ~3 min (no frames, no keepalive, no close — a "zombie" connection), and job.events() hung — still blocked minutes after the job had already completed. poll/wait/run were unaffected (the job itself finished fine).

Root cause

iterateSse read the fetch body with no idle timeout, so it blocks forever on a stalled-but-open connection. The high-level Job.events() reconnect/poll-fallback only runs when the stream ends (the async iterator returns or throws), which never happens for a zombie → events() hangs.

Fix

Add a byte-level read-idle timeout to iterateSse (default SSE_IDLE_TIMEOUT_MS, well above the server keepalive interval). It resets on any bytes — so keepalive comments (which eventsource-parser drops as non-messages) still count as liveness, and only a truly silent connection trips it. A stalled stream now errors, which Job.events() already catches and turns into a poll (terminal?) / reconnect.

Tests

Added a regression test: a stream that emits two frames then holds open + silent → iterateSse errors quickly (~idle timeout) instead of hanging, after delivering the pre-stall frames. Full suite green; tsc/oxfmt/hygiene clean.

🤖 Generated with Claude Code

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📒 Files selected for processing (2)

• src/low/sse.test.ts
• src/low/sse.ts

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