Add examples catalog with subcommand dispatch

- Extract game engine from package main to engine/ library package
- Create examples/ package with registry, Entry type, and BuilderDeps
- Register default world as an example (moved from main())
- Add combat example: two teams of units facing each other
- Rewrite main.go as thin dispatch: go run . example [name]
- Update README with examples catalog one-liner

1 files changed, 20 insertions, 0 deletions

diff --git a/examples/examples.go b/examples/examples.go
new file mode 100644
index 0000000..9e18d6b
--- /dev/null
+++ b/examples/examples.go
@@ -0,0 +1,20 @@
+package examples
+
+import (
+	"age_of_empires/engine"
+
+	"github.com/hajimehoshi/ebiten/v2/text/v2"
+)
+
+type BuilderDeps struct {
+	FaceSource  *text.GoTextFaceSource
+	UnitBuilder engine.EntityBuilder
+}
+
+type Entry struct {
+	Name        string
+	Description string
+	Build       func(*engine.Game, BuilderDeps)
+}
+
+var Registry = map[string]Entry{}