v1.2.0:5 — Gear (breathing, 1-5) replaces RPE as the effort field for cardio

Cardio exercises now log a breathing "Gear" (1-5, per Brian MacKenzie)
instead of RPE (6-10) as their effort field; strength keeps RPE. An exercise
counts as cardio when its equipment type is "cardio" or it carries the
"cardio" muscle group (isCardioExercise in lib/exerciseOptions), so the
Assault Bike (type "assault bike") qualifies.

New nullable SetLog.gear column added by the boot-time guarded ALTER in
docker_entrypoint.sh (additive, idempotent); plumbed through all 5 set-write
paths, the summary/edit views, and CSV/JSON import-export. Existing rpe data
is untouched and still displays. Program/AI target-RPE is unaffected.

proof-of-work/lib/exerciseOptions.ts

@@ -131,3 +131,19 @@ export function deriveTrackingFieldOptions(exercises: Exercise[]): Option[] {
 export function displayLabel(value: string): string {
   return titleCaseToken(value);
 }
+
+/**
+ * Cardio exercises log breathing "Gear" (1-5) instead of RPE (6-10) as their
+ * effort field. An exercise counts as cardio if its equipment type is "cardio"
+ * or it carries the "cardio" muscle group (e.g. Assault Bike, type
+ * "assault bike", is tagged cardio).
+ */
+export function isCardioExercise(exercise: {
+  type?: string | null;
+  muscleGroups?: string | null;
+}): boolean {
+  if (normalizeValue(exercise.type || "") === "cardio") return true;
+  return parseJsonArray(exercise.muscleGroups ?? null).some(
+    (group) => normalizeValue(group) === "cardio"
+  );
+}