port ujsx from Deno-only to cross-platform (Node/Bun/Deno)

Add npm project configuration (package.json, tsconfig.json, tsup, vitest)
matching the taskgraph_ts conventions. All source imports changed from .ts
to .js extensions for Node16 module resolution. Tests migrated from Deno.test
to vitest. Fixed strict type errors (noUncheckedIndexedAccess). Preserved
deno.json with sloppy-imports for dual Deno/Node compatibility.

Subpath exports: schema, h, reactive, context, events, pointer, host,
transform, jsx-runtime — plus barrel export at root.

Build: ESM + CJS dual output via tsup. 22 tests passing.

package.json

@@ -0,0 +1,149 @@
+{
+  "name": "@alkdev/ujsx",
+  "version": "0.1.0",
+  "description": "Universal JSX — runtime-agnostic reactive tree primitives with TypeBox schemas",
+  "type": "module",
+  "main": "./dist/mod.cjs",
+  "module": "./dist/mod.js",
+  "types": "./dist/mod.d.ts",
+  "exports": {
+    ".": {
+      "import": {
+        "types": "./dist/mod.d.ts",
+        "default": "./dist/mod.js"
+      },
+      "require": {
+        "types": "./dist/mod.d.cts",
+        "default": "./dist/mod.cjs"
+      }
+    },
+    "./schema": {
+      "import": {
+        "types": "./dist/core/schema.d.ts",
+        "default": "./dist/core/schema.js"
+      },
+      "require": {
+        "types": "./dist/core/schema.d.cts",
+        "default": "./dist/core/schema.cjs"
+      }
+    },
+    "./h": {
+      "import": {
+        "types": "./dist/core/h.d.ts",
+        "default": "./dist/core/h.js"
+      },
+      "require": {
+        "types": "./dist/core/h.d.cts",
+        "default": "./dist/core/h.cjs"
+      }
+    },
+    "./reactive": {
+      "import": {
+        "types": "./dist/core/reactive.d.ts",
+        "default": "./dist/core/reactive.js"
+      },
+      "require": {
+        "types": "./dist/core/reactive.d.cts",
+        "default": "./dist/core/reactive.cjs"
+      }
+    },
+    "./context": {
+      "import": {
+        "types": "./dist/core/context.d.ts",
+        "default": "./dist/core/context.js"
+      },
+      "require": {
+        "types": "./dist/core/context.d.cts",
+        "default": "./dist/core/context.cjs"
+      }
+    },
+    "./events": {
+      "import": {
+        "types": "./dist/core/events.d.ts",
+        "default": "./dist/core/events.js"
+      },
+      "require": {
+        "types": "./dist/core/events.d.cts",
+        "default": "./dist/core/events.cjs"
+      }
+    },
+    "./pointer": {
+      "import": {
+        "types": "./dist/core/pointer.d.ts",
+        "default": "./dist/core/pointer.js"
+      },
+      "require": {
+        "types": "./dist/core/pointer.d.cts",
+        "default": "./dist/core/pointer.cjs"
+      }
+    },
+    "./host": {
+      "import": {
+        "types": "./dist/host/config.d.ts",
+        "default": "./dist/host/config.js"
+      },
+      "require": {
+        "types": "./dist/host/config.d.cts",
+        "default": "./dist/host/config.cjs"
+      }
+    },
+    "./transform": {
+      "import": {
+        "types": "./dist/transform/registry.d.ts",
+        "default": "./dist/transform/registry.js"
+      },
+      "require": {
+        "types": "./dist/transform/registry.d.cts",
+        "default": "./dist/transform/registry.cjs"
+      }
+    },
+    "./jsx-runtime": {
+      "import": {
+        "types": "./dist/core/jsx-runtime.d.ts",
+        "default": "./dist/core/jsx-runtime.js"
+      },
+      "require": {
+        "types": "./dist/core/jsx-runtime.d.cts",
+        "default": "./dist/core/jsx-runtime.cjs"
+      }
+    }
+  },
+  "publishConfig": {
+    "access": "public"
+  },
+  "files": [
+    "dist"
+  ],
+  "scripts": {
+    "build": "tsup",
+    "build:tsc": "tsc",
+    "test": "vitest run",
+    "test:watch": "vitest",
+    "test:coverage": "vitest run --coverage",
+    "lint": "tsc --noEmit",
+    "prepublishOnly": "npm run build"
+  },
+  "keywords": [
+    "ujsx",
+    "jsx",
+    "reactive",
+    "signals",
+    "typebox",
+    "universal-jsx"
+  ],
+  "license": "MIT OR Apache-2.0",
+  "dependencies": {
+    "@alkdev/typebox": "^0.34.49",
+    "@preact/signals-core": "^1.14.1"
+  },
+  "devDependencies": {
+    "@types/node": "^22.0.0",
+    "@vitest/coverage-v8": "^3.2.4",
+    "tsup": "^8.5.1",
+    "typescript": "^5.7.0",
+    "vitest": "^3.1.0"
+  },
+  "engines": {
+    "node": ">=18.0.0"
+  }
+}