* fix(sse): bound active streams without terminal events
* fix(sse): derive the active-stream ceiling from the largest registered model budget
The watchdog is a hard lifetime cap that never resets on bytes, so a flat
15-minute default killed models the registry already allows to run for 20
minutes (the Codex entries declare timeoutMs: 1_200_000). The default is now
that maximum plus a one-minute margin, and a new test re-derives the maximum
from the registry so a future larger budget fails the gate instead of silently
re-opening the bug.
Co-authored-by: diegosouzapw <8016841+diegosouzapw@users.noreply.github.com>
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Co-authored-by: diegosouzapw <8016841+diegosouzapw@users.noreply.github.com>
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