long window: resolve the window ts overflow problem

**Bug Description**

same as #2177 but for long window

**Expected Behavior**

**Steps to Reproduce**

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The issue references #2177 for context on the window timestamp overflow problem specific to long windows. Start by examining the linked issue to understand the bug and the codebase's window handling logic. Look for files related to window computations, timestamp management, and overflow checks. Determine what 'long window' means in this system and how timestamps are represented and processed.

索引モデルが issue の本文から書いたものです。