feat(ci): add GitHub Actions CI workflow with test, typecheck, and build jobs

Add CI that runs tests, typecheck, and build verification on push/PR to master.
Include test script in package.json and new .github/workflows/ci.yml.

Adds:
- .github/workflows/ci.yml: CI workflow with test, typecheck, and build jobs
- package.json: test script entry

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

package.json

@@ -24,7 +24,8 @@
     "build:schema": "bun run script/build-schema.ts",
     "clean": "rm -rf dist",
     "prepublishOnly": "bun run clean && bun run build",
-    "typecheck": "tsc --noEmit"
+    "typecheck": "tsc --noEmit",
+    "test": "bun test"
   },
   "keywords": [
     "opencode",