fix: write one truth model per target, not alias

generate_truth named a narrowed model's directory after the target
as typed, so three aliases of one target wrote three copies, and
the pipeline rebuilt the slug by hand to diff it. One function now
names the directory from the canonical target for both.

scripts/pipeline.py

@@ -41,7 +41,13 @@ if sys.version_info < (3, 12):
     sys.exit(f"pipeline.py needs Python 3.12 or newer, this is {sys.version.split()[0]}")
 
 sys.path.insert(0, str(Path(__file__).parent))
-from common import ArtifactLockBusy, artifact_lock, hold_artifact_lock
+from common import (
+    ArtifactLockBusy,
+    artifact_lock,
+    hold_artifact_lock,
+    list_registered_platforms,
+    truth_target_dir,
+)
 
 
 def run(cmd: list[str], label: str) -> tuple[bool, str]:
@@ -253,9 +259,12 @@ def _truth_steps(args: argparse.Namespace, results: dict) -> bool:
     # the whole scrape.
     truth_dir = Path(args.output_dir) / "truth"
     if args.target:
-        truth_dir = truth_dir / re.sub(
-            r"[^a-z0-9]+", "-", args.target.strip().lower()
-        ).strip("-")
+        # generate_truth --all writes every registered platform's model.
+        truth_dir = Path(truth_target_dir(
+            str(truth_dir),
+            list_registered_platforms("platforms", include_archived=True),
+            args.target,
+        ))
 
     if args.with_truth or args.with_export:
         truth_cmd = [