fix(train): the wheel is learnt from rides GPS covered, whatever its size (ADR 0030, D56)

The measure was held to GPS making 90 % of the wheel's way at the
circumference taken, 2105 mm to start: a real wheel under some 1.9 m fell
short of it on every ride and was never learnt. A ride now measures where
precise fixes followed it for 95 % of its moving time, its quotient between
1 and 3 m as one typed may be.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Signed-off-by: Tizian 「ティツィアーン」 <raisondetredev@pm.me>

docs/adr/0030-halkyon-train.md

@@ -1187,10 +1187,10 @@ Strava. What was found, 27 Oct:
     progress and live speed are the wheel's where GPS made less than 90 % of the wheel's
     way (a turbo trainer, a tunnel, no fix), else GPS's (`usesWheel`, `rodeByWheel`).
     The circumference starts at 2105 mm (700×25C) and is learnt from rides with at least
-    2 km of GPS whose quotient falls between 1.5 and 2.5 m: the first sets it, each later
-    one moves it a quarter of the way (`measuredWheelMm`); one typed on the Record sheet
-    (1000 to 3000 mm) stays until cleared, which measures again. Auto-pause still follows
-    GPS alone on a trainer.
+    2 km of GPS covering the ride (D56) whose quotient falls between 1 and 3 m: the
+    first sets it, each later one moves it a quarter of the way (`measuredWheelMm`); one
+    typed on the Record sheet (1000 to 3000 mm) stays until cleared, which measures
+    again. Auto-pause still follows GPS alone on a trainer.
 - **D50 The instance's own map and searching for places** (recommended, the developer's
   but the search's region; 29 Oct; step 12, what D22, D23 and D44 left for later):
   - **Tiles** (12a): Protomaps' basemap (schema v4, zooms 0 to 15, ODbL, OpenStreetMap's
@@ -1416,6 +1416,14 @@ Strava. What was found, 27 Oct:
   written, and the other version is offered instead (`LoopFailed('another update')`).
   The relay's calls to Polar have timeouts, caps on their size and https on every
   hop, one fetch per file at a time, and a limit per person.
+- **D56 The wheel learnt from GPS that covered the ride** (recommended, the developer's;
+  30 Oct; revises D49's measure): a ride measures the wheel where precise fixes followed
+  it for 95 % of its moving time (gaps of 30 s at most count, a pause cuts), not where
+  GPS made 90 % of the wheel's way at the circumference taken: that held every wheel to
+  the one taken, so a real wheel under some 1.9 m (20", 24", a child's 16") was never
+  learnt from the 2105 mm a sensor starts with. Its quotient may fall between 1 and 3 m,
+  as one typed may (`measuredWheelMm`, `_gpsCovered`). A tunnel's straight line still
+  measures nothing. The distance still follows `usesWheel`, against the wheel as learnt.
 
 ## Consequences