🛡️ Sentinel: Fix integer overflow in TokenBucketLimiter

[google-labs-jules]

🛡️ Sentinel: [CRITICAL] Fix integer overflow in TokenBucketLimiter

Vulnerability: The refill logic calculated tokens to add using periodsElapsed * refillTokens. This multiplication could overflow long if the time elapsed was large enough (e.g., due to system time jump or extreme configuration), resulting in a negative number. This caused the refill logic to abort, leaving the bucket empty indefinitely (DoS).

Fix: Added a pre-check: if (periodsElapsed > capacity / refillTokens). If true, we skip multiplication and simply fill the bucket to capacity, preventing the overflow.

Verification: Added TokenBucketOverflowTest which simulates a massive time jump via reflection and asserts that the bucket correctly refills instead of failing. Verified with ./gradlew test.

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PR created automatically by Jules for task 9149623540971139298 started by @SpaceLeam

[google-labs-jules]

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