fix: selectDate not working with uncontrolled calendar and isDateUnavailable

[cycsmail]

Closes #7779

normalizeValue passed startDate (the start of the visible range) as the lower bound to previousAvailableDate. When you select a date that falls before the visible range, for example programmatically while a later month is shown, that search window is empty so the selection was always rejected and value stayed null. It only showed up when isDateUnavailable was set, since that's the path that goes through previousAvailableDate. The fix clamps the lower bound to the selected date when the date is before startDate, so a date outside the visible range can still be selected. In-range selection is unchanged.

✅ Pull Request Checklist:

• Included link to corresponding React Spectrum GitHub Issue.
• Added/updated unit tests and storybook for this change (for new code or code which already has tests).
• Filled out test instructions.
• Updated documentation (if it already exists for this component).
• Looked at the Accessibility Practices for this feature - Aria Practices

📝 Test Instructions:

Render an uncontrolled Calendar with isDateUnavailable, navigate to another month, then call selectDate with a date outside the visible range, it should now select instead of doing nothing. Added packages/react-stately/test/calendar/useCalendarState.test.ts covering selecting a date both before and after the visible range. The before-range test fails without this change and passes with it, and the existing react-aria calendar + Calendar/RangeCalendar suites still pass. Run yarn jest useCalendarState.

🧑 Your Project:

N/A

[snowystinger]

I made some changes to hit a little more surface area with tests and simplify the code to convey intent.

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