fix: preserve focus after controlled month changes

[gpbl]

Context

Changing the controlled month and selected values while a day has focus replaces that day button. Focus currently falls back to the document body and keyboard navigation stops.

Closes #3009.

Analysis

useFocus retains the CalendarDay from the previously visible month. Although calculateFocusTarget identifies the selected day in the new month, that target is only used for the roving tab index and is never promoted to the focused state. The replacement DayButton therefore never receives the focused modifier that triggers DOM focus.

Solution

• Reconcile a stale focused day with the calculated focus target when the previous day is no longer displayed.
• Leave focus unchanged when it has already moved outside the day grid.
• Add source and consumer-level regression coverage for both focus paths.
• Add an interactive ControlledMonthFocus example to the examples app.
• Add a patch changeset for react-day-picker and @daypicker/react.
• Validate all Jest projects, TypeScript, Biome, the examples-app production build, and the changeset release plan.

[changeset-bot]

🦋 Changeset detected

Latest commit: a8d8470

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 7 packages

Name	Type
react-day-picker	Patch
@daypicker/react	Patch
@daypicker/buddhist	Patch
@daypicker/ethiopic	Patch
@daypicker/hebrew	Patch
@daypicker/hijri	Patch
@daypicker/persian	Patch

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