feat(train): a ride's distance from the wheel where GPS falls short (ADR 0030, D49)

The speed sensor's wheel gives a ride's distance, splits, progress and live
speed where GPS made less than 90 % of its way (a turbo trainer, a tunnel);
its circumference starts at 2105 mm, is learnt from rides with 2 km of GPS
or typed on the Record sheet.

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

@@ -1180,8 +1180,17 @@ Strava. What was found, 27 Oct:
     power (Coggan's: the watts a second, the last reading held 5 s, their 30 s rolling
     mean, the fourth root of its fourth powers' mean; none under a minute) and the
     cadence's chart and average (coasting left out of the average); the files out carry
-    the crank's cadence and the watts. Not yet: the wheel's speed and distance (next),
-    Health Connect's power and cadence records. Not tried with a real sensor yet.
+    the crank's cadence and the watts. Not yet: Health Connect's power and cadence
+    records. Not tried with a real sensor yet.
+  - Built: 11d's wheel. The service writes the wheel's circumference a ride starts with
+    (`wheelsize` line, the `wheel` series' `mm` column); a ride's distance, splits,
+    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.
 
 ## Consequences