chore: standardize TypeScript version to 6.0.2 across workspace

- Updated pnpm-workspace.yaml to enforce TypeScript version 6.0.2.
- Replaced legacy TypeScript import with the current version in comparison tools.
- Added ignoreDeprecations setting in tsconfig.base.json to suppress deprecation warnings for baseUrl.
- Introduced TypeScript version policy documentation outlining the rationale and upgrade gate for moving to TypeScript 7.

package.json

@@ -31,8 +31,7 @@
         "prettier": "^3.9.6",
         "tsdown": "^0.22.14",
         "turbo": "^2.10.6",
-        "typescript": "^7.0.2",
-        "typescript-legacy": "npm:typescript@5.9.3",
+        "typescript": "6.0.2",
         "typescript-eslint": "^8.65.0",
         "vue-eslint-parser": "^10.4.1"
     }