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.

docs/testing-policy.md

@@ -47,6 +47,9 @@ information only, not evidence of correctness.
 - Validate domain constraints in the logic layer where possible; DB constraints
   act as a secondary safety net.
 - Use deterministic seeds for all gameplay-impacting RNG.
+- Run TypeScript validation with the workspace-standard TypeScript `6.0.2`.
+  TypeScript 5 or 7 results do not replace the required repository typecheck.
+  See `docs/architecture/typescript-version.md`.
 
 ## Test Layers