Read a store's config from the registry record

`GET /api/stores` records now carry a `config` field — a store's `config.json` moved
into the record that already said what the store is — and the client applies it
directly. Installing a store no longer depends on a second repository existing and
staying reachable, and a store can be configured from the site's admin alone.

The order is registry config, then a repository's `config.json`, then the engine's
defaults. The middle one is why nothing has to move at once: a registry whose stores
have not been migrated is read exactly as before.

The window cannot supply a config. It is handed stores to show and hands one back to
install, but only as an identity: `RegistryStoreDtoMapper.toModel` drops the config and
`StoreProvisioningService` reads the record again from the registry first. A config
decides where files are written and, through `paths.subfolder`, which subtree the store
may later delete from — not a decision the renderer gets to make, for the same reason a
`GameDto` carries no paths. Tested by installing from a record carrying
`subfolder: "ATTACKER"` and `install_root: "/tmp/pwned"` and finding neither on disk.

A store that has left the registry, or a registry that cannot be re-read, still
installs: it falls back to the engine's defaults rather than refusing.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/application/mappers/RegistryStoreDtoMapper.ts

@@ -16,12 +16,20 @@ export class RegistryStoreDtoMapper {
     return stores.map((store: RegistryStore): RegistryStoreDto => this.toDto(store))
   }
 
-  /** The window hands a record straight back when asking for an install. */
+  /**
+   * The window hands a record back when asking for an install — as an identity only.
+   *
+   * There is no `config` here on purpose. A store's config decides where files are
+   * written and which subtree the store may delete from, so it must not be something
+   * the window can supply; `StoreProvisioningService` reads the real record from the
+   * registry instead. That is the same rule as `GameDto` carrying no paths.
+   */
   public toModel (dto: RegistryStoreDto): RegistryStore {
     return {
       name: dto.name,
       catalogUrl: dto.catalogUrl,
-      storeRepositoryUrl: dto.storeRepositoryUrl
+      storeRepositoryUrl: dto.storeRepositoryUrl,
+      config: null
     }
   }
 }