Migrate legacy architecture heading during section upsert

scripts/render_prometheus_docs.py

@@ -429,8 +429,18 @@ def render_architecture_section(
 def upsert_generated_section(path: Path, section_markdown: str, dry_run: bool, verbose: bool) -> None:
     existing = path.read_text(encoding="utf-8") if path.exists() else ""
     section_body = section_markdown
+    legacy_heading = "## Runtime visibility from Prometheus"
+    new_heading = "## Runtime and infrastructure inventory"
 
     if GENERATED_BEGIN in existing and GENERATED_END in existing:
+        # Migration: replace legacy heading that exists outside the generated markers.
+        existing = re.sub(
+            rf"^{re.escape(legacy_heading)}(?=\n)",
+            new_heading,
+            existing,
+            count=1,
+            flags=re.MULTILINE,
+        )
         pattern = re.compile(
             rf"{re.escape(GENERATED_BEGIN)}.*?{re.escape(GENERATED_END)}",
             re.DOTALL,
@@ -438,7 +448,7 @@ def upsert_generated_section(path: Path, section_markdown: str, dry_run: bool, v
         replacement = "\n".join(
             line
             for line in section_body.splitlines()
-            if line.strip() not in {"## Runtime visibility from Prometheus", "## Runtime and infrastructure inventory"}
+            if line.strip() not in {legacy_heading, new_heading}
         )
         updated = pattern.sub(replacement.strip(), existing)
     else: