Generate application identity for backends and native hosts

[turinglambdaai]

Summary

• stage the
  ivet.rktd application identity in every build and expose it to Racket through the new
  ivet/app-info API
• generate display name, version, build, identifier, and release channel constants for Swift, C++, and Kotlin clients
• use the generated display name for scaffolded and reference macOS window titles
• make package verification reject missing, stale, or malformed staged identity metadata
• bound build numbers to the signed 64-bit range shared by all generated languages

This removes app-local version copies that can make update checks report the current release forever, while keeping
ivet.rktd as the single source of truth.

Validation

aco test tests/ — 8,635 tests passed

• focused app-info, codegen, project-validation, resource-verification, and documentation tests passed

Fixes #97
Fixes #102