Fixes #6185.

Every CI run of \ est.yml\ fails at \pnpm build\ since TypeScript 7.0.2 became npm's \latest\ (2026-07-08). \ ypescript@latest\ now resolves to the Go-native compiler, which no longer ships \ s.sys\ — and \zshy\ (used by \packages/zod\ and @zod/resolution) reads tsconfigs through \ s.sys.readFile, crashing with:

Build failed: TypeError: Cannot read properties of undefined (reading 'readFile')

Both matrix jobs go red for this one root cause (the 5.5 job is only cancelled by matrix fail-fast).

Two changes:

• Move \pnpm build\ above \pnpm add typescript@… -w\ so the repo-pinned TypeScript always runs the build; the matrix TS then applies only to the test/typecheck phase.
• Cap the matrix at TypeScript 6 (\5.5\ and \6) instead of \latest. TS 6 still ships the JS compiler API, so zshy builds and @zod/resolution's own zshy build both pass. This keeps broader coverage than pinning at 5, and the matrix can resume tracking \latest\ once zshy supports TS 7.