fix: record each platform's own list version

install/<platform>.json wrote the constant "1.0" as the version of the
list it was built from. The manifest now carries the version the platform
YAML records, and generate_pack refuses a YAML without one.

inherits: no longer passes a parent's version to a child: Lakka was
published as RetroArch v1.22.2 in its manifest, pack name and site page.
lakka.yml records v6.1, the Lakka-LibreELEC tag its target list is read
at. The MiSTer scraper refuses a BiosDB without a timestamp instead of
writing an empty version.

A pack's manifest.json records list_version, so an install from the pack
alone knows it too. Manifests regenerated twice and compared: only
version and generated changed.

scripts/scraper/misterfpga_scraper.py

@@ -215,12 +215,12 @@ class Scraper(BaseScraper):
             if not entry["docs"]:
                 del entry["docs"]
 
+        # The BiosDB has no release: the date it was built is the only
+        # version the list carries, and the manifest needs one.
         timestamp = data.get("timestamp")
-        released = (
-            datetime.fromtimestamp(timestamp, timezone.utc).strftime("%Y-%m-%d")
-            if isinstance(timestamp, (int, float))
-            else ""
-        )
+        if not isinstance(timestamp, (int, float)):
+            raise RuntimeError(f"{self.url}: the BiosDB records no timestamp")
+        released = datetime.fromtimestamp(timestamp, timezone.utc).strftime("%Y-%m-%d")
 
         return {
             "platform": "MiSTer FPGA",