refactor: read measurements from the local tree

The site compiles the index and the SQLite files from measurements/
instead of a pinned clone. The pin, the sync script, the CI clone steps,
the freshness area and its refresh handler are gone. core_probe --record
writes into measurements/ of the checkout by default, and a test fails
when a line or data file HEAD holds changed or vanished.

tests/test_site_r4_reference.py

@@ -248,32 +248,23 @@ class SourceLinksOnlyWhereTheFileIs(unittest.TestCase):
     def test_every_rendered_link_is_recorded(self):
         record = json.loads(sitesources.SOURCE_PATHS.read_text(encoding="utf-8"))
         pages = sorted(_built(DOCS / "emulators").rglob("*.md*")) + sorted(DOCS.glob("gaps*.md*"))
-        import sync_measurements  # noqa: PLC0415
+        import measurement_records  # noqa: PLC0415
 
-        # A Tested block links the measurements repository at its pin. The
-        # record of source trees does not cover it: those paths are checked
-        # against the pinned tree of the clone itself.
-        measured_slug = urllib.parse.urlsplit(sync_measurements.load_pin()["repo"]).path.strip("/")
-        measured: dict[str, set[str]] = {}
+        # A Tested block links a record line and its data file in this
+        # repository. The records are append-only, so a file a permalink
+        # names is still in the tree.
+        records = set(measurement_records.tree_files(REPO_ROOT))
         checked, stray = 0, []
         for page in pages:
             for found in _PERMALINK.finditer(page.read_text(encoding="utf-8")):
-                if "/Abdess/retrobios/" in found[0]:
-                    continue
                 key = f"{found['host']}/{found['slug']}@{found['pin']}"
                 path = urllib.parse.unquote(found["path"])
-                checked += 1
-                if found["slug"] == measured_slug:
-                    if found["pin"] not in measured:
-                        if not sync_measurements.has_commit(sync_measurements.CLONE, found["pin"]):
-                            stray.append((page.name, key, "pin not in the measurements clone"))
-                            measured[found["pin"]] = set()
-                            continue
-                        measured[found["pin"]] = set(
-                            sync_measurements.tree_files(sync_measurements.CLONE, found["pin"]))
-                    if path not in measured[found["pin"]]:
+                if "/Abdess/retrobios/" in found[0]:
+                    if path.startswith(f"{measurement_records.RECORDS_DIR}/") and path not in records:
                         stray.append((page.name, key, path))
-                elif path not in record.get(key, ()):
+                    continue
+                checked += 1
+                if path not in record.get(key, ()):
                     stray.append((page.name, key, path))
         self.assertGreater(checked, 1000)
         self.assertEqual(stray[:20], [])