fix(tsconfig): set explicit rootDir for TS6 builds

- Purpose: keep declaration builds working after the PR upgrades TypeScript from v5 to v6.
- Before: \tsconfig.json(8,25): error TS6046: Argument for '--moduleResolution' option must be: 'node', 'classic', 'node16', 'nodenext'.
tsconfig.json(9,5): error TS5023: Unknown compiler option 'allowImportingTsExtensions'.
tsconfig.json(10,5): error TS5070: Option '--resolveJsonModule' cannot be specified without 'node' module resolution strategy. inferred the common source directory and CI failed with TS5011 under TypeScript 6.
- Why that was a problem: the PR branch looked green locally with stale dependencies, but the actual CI environment installs the new compiler and the build stopped before publish.
- What this change accomplishes: it makes the source layout explicit so declaration emit remains stable on TypeScript 6.
- How it works: set \rootDir\: \src\ in \ to match the package entrypoints and output structure.

Author: elibosley

tsconfig.json

@@ -15,8 +15,9 @@
     "noUnusedParameters": true,
     "noFallthroughCasesInSwitch": true,
     "declaration": true,
+    "rootDir": "src",
     "outDir": "dist"
   },
   "include": ["src"],
   "exclude": ["src/__tests__"]
-} 
+}