Update specs: session-notes, route-coloring, gpx-import

session-notes: Reflect CodeMirror 6 editor with character-level sync,
remote cursor awareness, dedicated undo manager, awareness isolation.

route-coloring: Added grade color mode, moved toggle to chart, added
surface/grade chart coloring, legends for all modes, contextual hover.

gpx-import: Added day break preservation (overnight waypoints survive
GPX roundtrip).

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

openspec/specs/gpx-import/spec.md

@@ -40,3 +40,15 @@ The Planner SHALL reject non-GPX files dropped on the map.
 #### Scenario: Drop non-GPX file
 - **WHEN** a user drops a non-GPX file on the map
 - **THEN** the file is ignored with a brief error toast
+
+### Requirement: Day break preservation
+GPX import SHALL preserve overnight waypoint metadata for multi-day routes.
+
+#### Scenario: Import GPX with overnight waypoints
+- **WHEN** a GPX file contains waypoints with `<type>overnight</type>`
+- **THEN** the imported waypoints have their `isDayBreak` / `overnight` flag set in Yjs
+- **AND** the day breakdown appears in the sidebar
+
+#### Scenario: Import GPX with POI metadata
+- **WHEN** a GPX file contains waypoints imported from POI snap (with name)
+- **THEN** the waypoint name is preserved on import