fix: Rewrite profile example tests with demo-first structure

Restructure all four profile test files (R4 bodyweight, R4 BP,
US Core bodyweight, US Core BP) to follow the demo-first pattern:
readable demos on top, concise regression tests below.

Author: ryukzak

examples/typescript-r4/__snapshots__/profile-bodyweight.test.ts.snap

@@ -1,5 +1,45 @@
 // Bun Snapshot v1, https://bun.sh/docs/test/snapshots
 
+exports[`demo: create a bodyweight observation build a valid bodyweight resource step by step 1`] = `
+{
+  "category": [
+    {
+      "coding": [
+        {
+          "code": "vital-signs",
+          "system": "http://terminology.hl7.org/CodeSystem/observation-category",
+        },
+      ],
+    },
+  ],
+  "code": {
+    "coding": [
+      {
+        "code": "29463-7",
+        "system": "http://loinc.org",
+      },
+    ],
+  },
+  "effectiveDateTime": "2024-06-15",
+  "meta": {
+    "profile": [
+      "http://hl7.org/fhir/StructureDefinition/bodyweight",
+    ],
+  },
+  "resourceType": "Observation",
+  "status": "final",
+  "subject": {
+    "reference": "Patient/pt-1",
+  },
+  "valueQuantity": {
+    "code": "kg",
+    "system": "http://unitsofmeasure.org",
+    "unit": "kg",
+    "value": 75,
+  },
+}
+`;
+
 exports[`bodyweight profile creation fully populated resource matches snapshot 1`] = `
 {
   "category": [

examples/typescript-r4/__snapshots__/profile-bp.test.ts.snap

@@ -1,6 +1,6 @@
 // Bun Snapshot v1, https://bun.sh/docs/test/snapshots
 
-exports[`blood pressure profile fully populated resource matches snapshot 1`] = `
+exports[`demo: create a blood pressure observation build a valid BP resource step by step 1`] = `
 {
   "category": [
     {
@@ -10,7 +10,6 @@ exports[`blood pressure profile fully populated resource matches snapshot 1`] =
           "system": "http://terminology.hl7.org/CodeSystem/observation-category",
         },
       ],
-      "text": "Vital Signs",
     },
   ],
   "code": {
@@ -30,6 +29,8 @@ exports[`blood pressure profile fully populated resource matches snapshot 1`] =
         },
       },
       "valueQuantity": {
+        "code": "mm[Hg]",
+        "system": "http://unitsofmeasure.org",
         "unit": "mmHg",
         "value": 120,
       },
@@ -42,6 +43,8 @@ exports[`blood pressure profile fully populated resource matches snapshot 1`] =
         },
       },
       "valueQuantity": {
+        "code": "mm[Hg]",
+        "system": "http://unitsofmeasure.org",
         "unit": "mmHg",
         "value": 80,
       },
@@ -56,7 +59,7 @@ exports[`blood pressure profile fully populated resource matches snapshot 1`] =
   "resourceType": "Observation",
   "status": "final",
   "subject": {
-    "reference": "Patient/pt-2",
+    "reference": "Patient/pt-1",
   },
 }
 `;