Fix: prevent widget getting stuck at #/all when navigating forecast dates

[rchlfryn]

Description

Fixes a race condition in WidgetRouterHandler that caused the widget to get stuck at #/all during zone-date-zone navigation. The issue occurred when useHash's setTimeout-delayed state captured intermediate widget routing states instead of the final hash value we wanted

Related Issues

Fixes #918

Key Changes

WidgetRouterHandler.client.tsx:

• Changed to read window.location.hash directly instead of using observedHash state
• observedHash still triggers the effect when hash changes, but we always read the current hash value
• This ensures validation happens against the actual current hash, not a stale React state value

How to test

1. Navigate to any zone forecast page (e.g., /forecasts/avalanche/olympics)
2. Use the date navigation in the widget to view previous/next forecasts
3. Navigate to a different zone forecast page
4. Expected: Smooth navigation between zones and display selected zone information
5. Bug (before fix): Widget would load all forecast information at #/all while URL showed correct place

Also test:

• Zone-to-zone navigation still works
• Initial page load sets correct hash
• No infinite loops or console errors

Screenshots / Demo video

https://www.loom.com/share/d0b89b8ff5774699b0e5294381742ffe

[github-actions]

Preview deployment: https://bug-avy-forecast-nav.preview.avy-fx.org