ts-node 10.x is incompatible with the TypeScript 7 compiler API (cdk synth
fails with "Cannot read properties of undefined (reading 'fileExists')").
Swap the cdk.json app runner from ts-node to tsx, drop ts-node, pin tsx to
4.23.0 (matching sh-mcp), and bump typescript to ~7.0.2. Verified via
cdk synth (exit 0) and tsc build.