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.py

@@ -16,6 +16,7 @@ from castle_core.manifest import (
     HttpExposeSpec,
     HttpInternal,
     ProgramSpec,
+    Reach,
     RunPython,
     SystemdDeployment,
 )
@@ -157,7 +158,7 @@ def _service(port: int, *, expose: bool) -> SystemdDeployment:
         manager="systemd",
         run=RunPython(launcher="python", program="svc"),
         expose=ExposeSpec(http=HttpExposeSpec(internal=HttpInternal(port=port))),
-        proxy=expose,
+        reach=Reach.INTERNAL if expose else Reach.OFF,
     )