fix portable ChatGPT desktop launching

[irasutoya]

What changed

• restrict AppX activation to Codex installations that are actually inside a WindowsApps directory
• launch unpacked/portable packages directly through ChatGPT.exe or Codex.exe
• recognize portable ChatGPT.exe processes after Codex was merged into ChatGPT Desktop
• add regression coverage for unpacked package-shaped directories and portable ChatGPT process detection

Root cause

An unpacked MSIX keeps a directory name such as OpenAI.Codex_<version>_x64__<publisher>. Codex++ inferred the App User Model ID from that name alone and attempted IApplicationActivationManager activation. A portable copy is not registered with Windows, so activation fails even though its ChatGPT.exe is directly runnable.

The process watcher also deliberately accepted local Codex.exe but excluded local ChatGPT.exe, which no longer matches the merged desktop app layout.

User impact

Users can select and launch a portable/unpacked Codex/ChatGPT Desktop build whose entry point is ChatGPT.exe, while Microsoft Store installs continue to use packaged activation.

Validation

• cargo fmt --check
• git diff --check
• Added focused launcher and watcher regression tests