Add SmartSentinels Alerts

[Montoya]

This closes #1484

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Note

Low Risk
Low risk: adds a new entry to the signed registry.json with metadata and a version checksum, without changing validation or runtime logic.

Overview
Adds npm:smartsentinels-alerts to src/registry.json, including its directory metadata (name, author, category, support/source links, description) and an initial 0.1.1 version pinned by checksum.

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