on_session_reset() cleared _previous_summary, _last_summary_error, and
_ineffective_compression_count but left _summary_failure_cooldown_until
intact. When a transient summary error sets a 60 s cooldown (or 600 s
for a missing-provider RuntimeError) and the user immediately runs /reset
or /new, the cooldown carries into the new session. If the new session
reaches the compression threshold before the cooldown expires,
_generate_summary() returns None early, middle turns are silently dropped
without a summary, and the agent continues with no indication that
compaction was skipped.
Fix: set _summary_failure_cooldown_until = 0.0 in on_session_reset(),
matching the value assigned in __init__ and symmetric with the other
per-session fields already cleared there.
Fixes#15547
e2211b2683