Now I have a complete picture of the changes. Let me do my final analysis:

Summary of the PR:

• Adds scheduledTime (as a double milliseconds-since-epoch) to AlarmInvocationInfo, which is the object passed to Durable Object alarm handlers.
• The value is converted from kj::Date (nanoseconds) to milliseconds via integer division, then stored as double. This is consistent with how ScheduledEvent.scheduledTime works.
• TypeScript types are updated correctly.
• Test coverage validates the new property.

Analysis:

1. Backward compatibility: This is purely additive — a new read-only property on an existing object. Existing alarm handlers that don't access scheduledTime are completely unaffected. No compat flag needed.

2. Safety: scheduledTime is captured by value (it's a kj::Date, wrapping int64_t), so the lambda capture is safe. No lifetime issues.

3. Precision: The static_cast<double> of milliseconds-since-epoch is fine for any practical date (loss only beyond ~285,000 years from epoch).

4. Type snapshots: All four generated snapshot files are updated consistently.

5. Test: The test stores the time passed to setAlarm and verifies it matches alarmInfo.scheduledTime in the handler. This is a good end-to-end validation.

6. JSG_READONLY_INSTANCE_PROPERTY: Technically the project convention prefers prototype properties, but the pre-existing isRetry and retryCount already use instance properties. Being consistent with the existing class is the right call here.

This is a clean, well-scoped change with no issues to flag.

LGTM

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