test(apilive): run the provenance assertions as subtests

The subtest gate caught a loop the reader tests added: a range over the strings
a provenance line must contain, asserting without opening one subtest per case.

Each of those strings is a separate claim about what a reader needs from that
line, so a failure should name which one is missing rather than which loop
failed. That is the whole reason for the rule.

Author: jmrplens

README.md

@@ -468,9 +468,9 @@ and is never logged. Full details: [PRIVACY.md](PRIVACY.md).
 | Category                 |     Files |       Lines |
 | ------------------------ | --------: | ----------: |
 | Source (`.go`, non-test) |     1,238 |     261,151 |
-| Unit tests (`_test.go`)  |       726 |     424,800 |
+| Unit tests (`_test.go`)  |       726 |     424,803 |
 | End-to-end tests         |       246 |      66,332 |
-| **Total**                | **2,210** | **752,283** |
+| **Total**                | **2,210** | **752,286** |
 
 ### Functions
 
@@ -480,7 +480,7 @@ and is never logged. Full details: [PRIVACY.md](PRIVACY.md).
 | . Exported (public)             |  2,989 |
 | . Unexported (private)          |  6,607 |
 | Unit test functions (`TestXxx`) | 14,434 |
-| Subtests (`t.Run(...)`)         |  5,776 |
+| Subtests (`t.Run(...)`)         |  5,777 |
 | End-to-end test functions       |    605 |
 
 ### Ratios worth noting

cmd/internal/apilive/join_test.go

@@ -389,9 +389,12 @@ func TestSourceString_TheProvenanceLineAGateReports(t *testing.T) {
 	}.String()
 
 	for _, want := range []string{"582 entities", "7317 fields", "2110 routes", "264 licensed features", "19.3.1-ee", "2026-09-09"} {
-		if !strings.Contains(line, want) {
-			t.Errorf("provenance line %q is missing %q", line, want)
-		}
+		t.Run(want, func(t *testing.T) {
+			t.Parallel()
+			if !strings.Contains(line, want) {
+				t.Errorf("provenance line %q is missing %q", line, want)
+			}
+		})
 	}
 }