chore: upgrade to TypeScript 7

[corwinm]

Summary

• upgrade the TypeScript dev dependency from ^5.9.3 to stable ^7.0.2
• refresh the npm lockfile for TypeScript 7's platform-specific compiler packages
• keep source and compiler configuration unchanged

Validation

• npm ci
• npm run ci
  • npm run typecheck
  • npm run test (7 files, 58 tests passed)
  • npm run pack:all (clean build plus dry-run packs for all 4 workspaces)
• npm audit --omit=dev (0 production vulnerabilities)
• compared TypeScript 5.9.3 and 7.0.2 declaration output
  • all declaration maps and all but one declaration file were byte-identical
  • the sole difference only reorders properties in inferred union members in pi-copy-code-block; exported types and package contents are otherwise unchanged
• rebuilt all packages with the installed TypeScript 7.0.2 compiler after the comparison