feat: build pipeline — .ts → .esm.js + .yaml + .d.ts 三件套

- add command auto-detects .ts vs .esm.js input
- .ts: Bun.build → bundle + descriptor extraction + JSON Schema → .d.ts
- .esm.js: requires .yaml alongside, .d.ts optional
- JSON Schema → TypeScript type converter
- hello-world example workflow
- 63 tests pass, biome clean

Closes #7
小橘 <xiaoju@shazhou.work>

biome.json

@@ -38,6 +38,16 @@
           }
         }
       }
+    },
+    {
+      "includes": ["examples/**/*.ts", "packages/workflow/__tests__/fixtures/**/*.ts"],
+      "linter": {
+        "rules": {
+          "style": {
+            "noDefaultExport": "off"
+          }
+        }
+      }
     }
   ],
   "linter": {