fix(targets): no adult weight and BMI bands on a child's record

Now that the BMI chart draws inside a managed record, a child's normal
BMI sat in the red under-17 band, and the weight page painted the adult
WHO band (about 26 to 35 kg for 118 cm), so a healthy 21 kg read as
underweight. The release's own weight-band test pinned that band.

No band here knows a child's age yet. For a record under 18, or a
managed record with no date of birth, the targets read names no WHO
weight range, no BMI range and no category; the record's own weight
target still shows, and the values and the chart stay. The BMI chart
and the weight band draw only what the server names. The weight-band
test now uses an adult height and gains the child case.

The targets builder and the vitals builder grow by two lines each for
the flag; their size baselines are raised to match.

src/__tests__/baselines/source-function-lines.json

@@ -331,8 +331,8 @@
     "lib/record-activity/activity-verb.ts :: recordActivityVerbLine": 261,
     "lib/strava/sync.ts :: runStravaSync": 219,
     "lib/support/report.ts :: collectSupportReportFacts": 332,
-    "lib/targets/build-response.ts :: buildTargetsResponse": 330,
-    "lib/targets/vitals-builder.ts :: buildVitalTargets": 324,
+    "lib/targets/build-response.ts :: buildTargetsResponse": 332,
+    "lib/targets/vitals-builder.ts :: buildVitalTargets": 326,
     "lib/telegram-webhook-handlers.ts :: handleCallback": 582,
     "lib/telegram-webhook-handlers.ts :: handleTextMessage": 322,
     "lib/withings/sync-activity.ts :: syncUserActivity": 377,