Sync notes through GPX, Journal, and Planner roundtrip

Full notes lifecycle:
- GPX: description field in GpxData, <metadata><desc> in generate/parse
- Export: Plan GPX and Save to Journal include notes as description
- Journal: updateRoute extracts description from GPX, stores on route
- Reimport: Edit in Planner passes notes via URL params → Yjs Y.Text
- Drop import: GPX with <desc> restores notes in session

Spec updated: session-notes gains GPX export, Journal sync, and
reimport requirements.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/journal/app/routes/api.routes.$id.edit-in-planner.ts

@@ -37,6 +37,7 @@ export async function action({ params, request }: Route.ActionArgs) {
     url: string;
     initialWaypoints?: Array<{ lat: number; lon: number; name?: string }>;
     initialNoGoAreas?: Array<{ points: Array<{ lat: number; lon: number }> }>;
+    initialNotes?: string;
   };
 
   // Encode planning data in URL params
@@ -47,6 +48,9 @@ export async function action({ params, request }: Route.ActionArgs) {
   if (session.initialNoGoAreas?.length) {
     urlParams.set("noGoAreas", JSON.stringify(session.initialNoGoAreas));
   }
+  if (session.initialNotes) {
+    urlParams.set("notes", session.initialNotes);
+  }
 
   return data({
     url: `${plannerUrl}${session.url}?${urlParams}`,