✨ 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

tsconfig.json

@@ -1,39 +1,21 @@
 {
+    "extends": [
+        "@tsconfig/node26/tsconfig.json",
+        "@tsconfig/strictest/tsconfig.json"
+    ],
     "compilerOptions": {
         "noEmit": true,
         "target": "es2024",
-        "module": "nodenext",
-        "moduleResolution": "nodenext",
-        "moduleDetection": "force",
         "lib": ["es2024"],
-        "skipLibCheck": true,
-        "strict": true,
-        "noImplicitAny": true,
-        "noImplicitThis": true,
-        "alwaysStrict": true,
-        "strictNullChecks": true,
-        "strictFunctionTypes": true,
-        "strictBindCallApply": true,
-        "strictPropertyInitialization": true,
-        "noImplicitReturns": true,
-        "noFallthroughCasesInSwitch": true,
-        "noUncheckedIndexedAccess": true,
-        "noImplicitOverride": true,
-        "forceConsistentCasingInFileNames": true,
-        "noUnusedLocals": true,
-        "noUnusedParameters": true,
-        "isolatedModules": true,
         "verbatimModuleSyntax": true,
         "allowImportingTsExtensions": true,
         "declaration": true,
         "declarationMap": true,
         "sourceMap": true,
         "outDir": "dist",
-        "esModuleInterop": true,
         "allowSyntheticDefaultImports": true,
         "resolveJsonModule": true,
-        "composite": false,
-        "types": ["node"]
+        "composite": false
     },
     "include": ["src"]
 }