feat(train): a route's line pulled out into a new waypoint, and any waypoint taken off (ADR 0030, D59)

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

@@ -1457,6 +1457,18 @@ Strava. What was found, 27 Oct:
   (`tool/release/fdroid/metadata/app.halkyon.train.yml`) declares `NonFreeDep` (Polar's
   SDK, D36) and `NonFreeNet` (Polar's firmware service, the direct way of D40, and the
   server's SSPL, as Learn's says).
+- **D59 Waypoints pulled out of the line, and any one taken off** (recommended, the
+  developer's; 30 Oct; D44): the planned line held and dragged pulls a waypoint out of
+  it, inserted between the two waypoints of the stretch it was held on, and the way is
+  planned again through it, as Komoot, brouter-web and Google Maps do; a waypoint tapped
+  offers to take it off, where undo took only the last. Held first, as a waypoint is
+  moved, so that dragging the map never pulls the line. Over a tap on the line
+  inserting a waypoint to be dragged after (two steps, and a line easily hit by a
+  finger meaning the map) and over a list of waypoints under the map (good for long
+  routes, clumsy for "a little closer to the lake"). The stretch is the one of the line
+  nearest where it was held, each waypoint's place on the line found from the one
+  before's on, so a way out and back the same streets keeps its stretches in order
+  (`insertionIndex`, `route_legs.dart`).
 
 ## Consequences