Fix all OpenSpec validation failures (36/36 passing)

- Add ## Purpose sections and convert delta headers to ## Requirements
  on all 25 specs
- Add SHALL keywords to requirements missing them (gpx-import,
  planner-session, planner-journal-handoff)
- Convert prose GPX format section to proper scenarios (no-go-areas)
- Create specs/ delta files for 7 changes that were missing them
  (activity-photos, local-dev-stack, multi-day-routes, route-discovery,
  route-sharing, visual-redesign, waypoint-notes)

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

openspec/changes/route-sharing/specs/route-sharing/spec.md

@@ -0,0 +1,38 @@
+## ADDED Requirements
+
+### Requirement: Route visibility
+Routes and activities SHALL support private (default) and public visibility levels.
+
+#### Scenario: Set route public
+- **WHEN** a route owner toggles visibility to "public"
+- **THEN** the route is viewable by anyone with the link
+
+#### Scenario: Default private
+- **WHEN** a new route is created
+- **THEN** its visibility is "private" (owner-only)
+
+### Requirement: Per-user route sharing
+Route owners SHALL be able to share routes with specific users at view or edit permission levels.
+
+#### Scenario: Share with user
+- **WHEN** a route owner shares a route with another user at "view" level
+- **THEN** the shared user sees the route in their collection and can view it
+
+#### Scenario: Edit permission
+- **WHEN** a route owner shares a route with "edit" permission
+- **THEN** the shared user can update the route name, description, and GPX
+
+### Requirement: Route forking
+Logged-in users SHALL be able to fork any public route into their own collection.
+
+#### Scenario: Fork public route
+- **WHEN** a user clicks "Fork" on a public route
+- **THEN** a copy of the route metadata and latest GPX is created in their collection
+- **AND** a `forkedFromId` link references the original route
+
+### Requirement: Contributor tracking
+Route versions SHALL record the identity of the contributor who saved them.
+
+#### Scenario: Planner callback contributor
+- **WHEN** the Planner saves back to the Journal via JWT callback
+- **THEN** the contributor's identity is recorded on the new route version