core: drop pre-migration read-compat now both nodes are current-format

Both machines (civil, primer) are on the current on-disk layout, so the
read-compat for older formats is dead weight. Remove it:

- config loader: only deployments/<kind>/<name>.yaml (drop flat deployments/*.yaml
  and the services/+jobs/ split); drop the run.runner→manager normalizer.
- registry loader: require composite <kind>/<name> keys + manager/kind (registry.yaml
  is regenerated every apply, so it's always current).
- manifest: drop the proxy/public→reach legacy input and the component→program alias
  (the derived proxy/public read accessors stay). reach field defaults already match.
- config_editor: parse incoming specs directly (frontend sends the current shape).
- save_config: drop the flat-file migration cleanup.

Bootstrap seeds move to bootstrap/deployments/<kind>/ and install.sh seeds that
per-kind tree directly. The legacy→current translation for terse test fixtures
moves into each test conftest (out of production). All suites green (362).

core/tests/test_caddyfile_remote.py

@@ -12,8 +12,8 @@ from castle_core.registry import Deployment, NodeConfig, NodeRegistry
 
 def _config_requiring_widget(root: Path) -> None:
     (root / "castle.yaml").write_text(yaml.safe_dump({"gateway": {"port": 18000}}))
-    svc_dir = root / "services"
-    svc_dir.mkdir()
+    svc_dir = root / "deployments" / "services"
+    svc_dir.mkdir(parents=True)
     (svc_dir / "consumer.yaml").write_text(
         yaml.safe_dump(
             {