chore(deps): typescript 6 (#23)

TS 7.0.2 exists but typescript-eslint rejects it — canaried and blocked;
revisit when support ships.


Claude-Session: https://claude.ai/code/session_01WqKqMnHQHSmkGFfc5t7Rxn

Co-authored-by: Mao Nakamoto <41178744+maonakamoto@users.noreply.github.com>
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

Author: catomean

package-lock.json

@@ -55,7 +55,7 @@
     "eslint": "^10.9.1",
     "globals": "^15.15.0",
     "prettier": "3.9.6",
-    "typescript": "^5.8.2",
+    "typescript": "^6.0.3",
     "typescript-eslint": "^8.68.0"
   }
 }