Add single-source loading and version checks

README.md

@@ -2,9 +2,28 @@
 
 An opinionated Go library for applications that use YAML configuration files.
 
-ConfigKit is in early implementation. The Go module and root package boundary are
-established, but no usable configuration loader has been implemented yet.
+ConfigKit is in early implementation. Its current loader accepts one strict YAML
+source (or explicit defaults-only input), applies typed defaults, optionally checks
+an application schema version, and returns detached metadata and safe diagnostics.
+Composition, profiles, application callbacks, overrides, secrets, and rendering are
+still under development.
 
-The [initial target design](docs/roadmap/initial.md) describes planned behavior.
+```go
+type Config struct {
+    Enabled bool `yaml:"enabled"`
+    Workers int  `yaml:"workers"`
+}
+
+func ReadConfig(path string) (Config, error) {
+    result, err := configkit.Load[Config](configkit.File(path))
+    if err != nil {
+        return Config{}, err
+    }
+    return result.Config, nil
+}
+```
+
+The [configuration contract](docs/config.md) describes implemented behavior. The
+[initial target design](docs/roadmap/initial.md) describes planned behavior.
 The [implementation plan](docs/roadmap/implementation.md) owns the pending stages.
 See the [development guide](docs/development.md) for repository orientation.