GNSS App: a Compass, with Places to be led back to and a level

Tab goes on from the Sky to a third view (issue #16): a rose that turns
with the device, the heading, where north came from and how long ago,
the sun on the rose, and a level. m marks where you stand as a Place,
t picks one as the target: an arrowhead on the rose, its distance and
bearing. The sensor's directions were checked by hand on the device.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0162FokPdvY2KsS4NBfwyWPk

CONTEXT.md

@@ -64,6 +64,17 @@ _Avoid_: lock, signal
 A route recorded from GNSS positions to a GPX file on the SD card, started and stopped by the user.
 _Avoid_: trace, log (a Log is recorded on its own)
 
+**Compass**:
+The third view of the GNSS App: a rose turned by the Heading, and the way to the target Place.
+
+**Heading**:
+Where the top of the device points, in degrees from true north. It is given by the course over ground while walking or by aiming at the sun, and held by the gyroscope in between.
+_Avoid_: course (the course is the direction of travel, from the receiver), bearing (a bearing is the direction to somewhere else)
+
+**Place**:
+A named position the user marked, kept as a GPX waypoint on the SD card, that the Compass can lead back to.
+_Avoid_: waypoint, POI
+
 **Wi-Fi Service**:
 The Service that owns the Wi-Fi radio. It's always in exactly one mode: *Off*, *Connected* (joined to a Saved Network) or *Monitoring* (passively observing). When Wi-Fi is enabled in Settings, it stays Connected whenever a Saved Network is in range. It goes Monitoring only while Wi-Fi Tools needs it, then reconnects.
 _Avoid_: network manager