chore(release): v0.2.7 — honest pins, visible managed model, physical delete

- A pinned playground model that is unavailable now errors clearly instead of
  silently answering from the managed local model (route_source no longer lies).
- The managed CMF model is surfaced in GET /admin/api/models (marked "managed",
  shown read-only in the UI) so the real running model is visible and pinnable
  without a hand-maintained [[models]] entry; a fresh install still lists nothing.
- Deleting a model now removes its local .cmf physically (file or tensor-dir);
  deleting the managed model also stops the server and clears the [cmf] config.
  Routing is stripped of the deleted id so the config still validates.

Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "cortiq-gateway"
-version = "0.2.6"
+version = "0.2.7"
 edition = "2021"
 rust-version = "1.75"
 license = "Apache-2.0"