Restore trip-change notification tap into the directions focus

[bmander]

Background

PR #1872 restructures the trip planner so directions are embedded in the home map (a "directions focus") and retires the standalone TripPlanScreen. That standalone screen used to consume a notification intent via TripPlanScreen.maybeRestoreFromIntent to rehydrate the form and show fresh results when the user tapped a "your trip changed" alert.

With the standalone screen gone, that restore path is now a no-op: the change notification still carries the serialized request (copyIntoBundleSimple) and the updated itineraries (OTPConstants.ITINERARIES) plus OTPConstants.INTENT_SOURCE = NOTIFICATION, but nothing in HOME reads those extras. Tapping a trip-change alert therefore opens generic HOME instead of the changed trip.

See TripPlanMonitorService.notifyChange (the openIntent around the copyIntoBundleSimple / ITINERARIES extras) — the code comment there marks the restore as deferred, and the PR body flags it as out of scope for that presentation-only change.

What's needed

Wire the notification tap into the new directions focus:

• Consume the launch intent in HOME (HomeActivity launch-intent channel → HomeViewModel.enterDirections(...)).
• Rehydrate the trip-plan form from the request bundle (mirroring the old maybeRestoreFromIntent).
• Inject the notification's precomputed itineraries into the directions results rather than re-planning.
• Preserve the INTENT_SOURCE = NOTIFICATION source metadata.

Notes

• Regression relative to pre-Trip planner: map-overlay layout (top-sheet form + bottom-sheet directions) #1872 behavior (the standalone screen restored the trip).
• Itineraries ride as JSON (kotlinx.serialization), not Serializable extras — the consuming side must decode with TripItinerary from JSON.

Deferred follow-up from PR #1872.