Add MAX_RECOVERY_ATTEMPTS (3) guard to post-compaction degradation recovery.
On models like Kimi/Minimax that repeatedly generate no-text responses,
the recovery loop would trigger indefinitely as each compaction reset the
recovery counter via onSessionCompacted.
The recovery count now persists across compaction cycles per session and
is only reset on session deletion (clear()), not on every compaction.
YeonGyu-Kim