ts-node 10.x is incompatible with the TypeScript 7 compiler API (cdk synth
fails with "Cannot read properties of undefined (reading 'fileExists')").
Switch the cdk.json app runner to tsx (pinned 4.23.0, matching sh-mcp) and
bump typescript to ~7.0.2. Synthesized templates are byte-identical across
all six stacks; toolchain-only change.