fix: measure separator gap presence in stint inference (CM-1143)

[skwowet]

Summary

Fixed an edge case in member organization stint inference where long-running concurrent orgs could incorrectly split an existing email-domain stint.

Previously, the separator check looked at whether another org's start or end date landed in the gap between the closest same-org stint and the new activity date. That caused false splits when a concurrent org overlapped the same-org stint for a long time but ended shortly after it.

The new logic treats another org as a separator only when it has meaningful presence in the gap. It also ignores umbrella/concurrent orgs that fully wrap the closest same-org stint.

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Note

Medium Risk
Changes the stint-splitting heuristic used by the cron-driven inference, which can alter generated member-organization date ranges and downstream reporting. Logic is localized but affects data updates/inserts based on historical activity gaps.

Overview
Updates inferMemberOrganizationStintChanges separator detection to split stints only when another organization has >30 days of actual overlap within the gap between the closest same-org stint and the new activity date.

Ignores concurrent "umbrella" org stints that fully wrap the neighbor stint and replaces the prior boundary-date check (start/end landing in the gap) with an explicit gap-overlap calculation, reducing false splits from long-running overlapping orgs.

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[Copilot]

Pull request overview

This PR adjusts the separator detection logic inside inferMemberOrganizationStintChanges to prevent incorrect splitting of an existing email-domain stint when another organization overlaps for a long time but only slightly extends into the gap.

Changes:

• Reworks “separator” detection to require >30 days of actual overlap within the computed gap between the closest same-org stint and the new activity date.
• Adds logic to ignore “umbrella” stints (other orgs) that fully wrap the closest same-org stint, treating them as concurrent rather than separators.

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