✨ Extend tsconfig from @tsconfig/node26 and @tsconfig/strictest

- Replace hand-rolled strict flags with @tsconfig/strictest
- Pick up Node 26 module/lib/target from @tsconfig/node26
- Add exactOptionalPropertyTypes (the main strictness gain)
- Pin target to es2024 to remain conservative for the published build

package.json

@@ -50,6 +50,8 @@
         "use:git-commit-message": "cp commit-message-template .git/COMMIT_EDITMSG || true"
     },
     "devDependencies": {
+        "@tsconfig/node26": "^26.0.1",
+        "@tsconfig/strictest": "^2.0.8",
         "@types/node": "^26.4.1",
         "c8": "^12.0.0",
         "check-outdated": "^3.0.0",
@@ -80,5 +82,8 @@
     },
     "engines": {
         "node": ">=26"
+    },
+    "allowScripts": {
+        "lefthook@2.1.12": true
     }
 }