feat: fix waypoint duplication on panel reopen & improve delete button enablement

[ritgit24]

Closes #270 & #365

🛠️ Fixes Issue

• Waypoints piling up on sidebar upon closing and reopening : Opening/closing left panel repeatedly appended empty waypoints, causing duplicates.
• Wrong Delete Waypoint enablement : Delete button on a waypoint was clickable even when that waypoint had no selected geolocation , if atleast one other waypoint was selected with a location.

Both the issues were potentially causing bad UX.

👨‍💻 Changes proposed

• use-directions-queries.ts : Ensuring waypoint slots exist before writing placeholders (prevents duplicated waypoints on sidebar reopen) by making permalink reverse‑geocode idempotent.

• waypoint-item.tsx : Only enable per‑waypoint Delete when that waypoint’s geocodeResults contains a selected result.

Test Updates

• waypoint-item.spec.tsx , waypoints.spec.tsx , directions.spec.tsx : Tp align mocks/expectations with new behavior.

📷 Screenshots