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.

deno.lock

@@ -0,0 +1,46 @@
+{
+  "version": "5",
+  "specifiers": {
+    "jsr:@std/assert@1": "1.0.19",
+    "jsr:@std/internal@^1.0.12": "1.0.12",
+    "npm:@alkdev/typebox@*": "0.34.49",
+    "npm:@preact/signals-core@*": "1.14.1"
+  },
+  "jsr": {
+    "@std/assert@1.0.19": {
+      "integrity": "eaada96ee120cb980bc47e040f82814d786fe8162ecc53c91d8df60b8755991e",
+      "dependencies": [
+        "jsr:@std/internal"
+      ]
+    },
+    "@std/internal@1.0.12": {
+      "integrity": "972a634fd5bc34b242024402972cd5143eac68d8dffaca5eaa4dba30ce17b027"
+    }
+  },
+  "npm": {
+    "@alkdev/typebox@0.34.49": {
+      "integrity": "sha512-hMidpI6GlMgQMlW9KEd8I3ywgewV6mva9iJaDuBfGtgeRAGrB8yyu6T/fHmgmyQineZ8l4/1PdH/VNr3S2er2g=="
+    },
+    "@preact/signals-core@1.14.1": {
+      "integrity": "sha512-vxPpfXqrwUe9lpjqfYNjAF/0RF/eFGeLgdJzdmIIZjpOnTmGmAB4BjWone562mJGMRP4frU6iZ6ei3PDsu52Ng=="
+    }
+  },
+  "workspace": {
+    "dependencies": [
+      "jsr:@std/assert@1",
+      "npm:@alkdev/typebox@*",
+      "npm:@preact/signals-core@*"
+    ],
+    "packageJson": {
+      "dependencies": [
+        "npm:@alkdev/typebox@~0.34.49",
+        "npm:@preact/signals-core@^1.14.1",
+        "npm:@types/node@22",
+        "npm:@vitest/coverage-v8@^3.2.4",
+        "npm:tsup@^8.5.1",
+        "npm:typescript@^5.7.0",
+        "npm:vitest@^3.1.0"
+      ]
+    }
+  }
+}