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

[BigPizzaV3]

Codex++ maintainer review note

Review finding: portable ChatGPT.exe process matching is too broad.

This PR changes find_codex_processes_from_snapshot to accept every local/portable ChatGPT.exe by exe name alone. On current main there is already a Windows regression test that intentionally keeps D:\Portable\ChatGPT\ChatGPT.exe out of find_codex_processes_from_snapshot while still blocking session-index cleanup. With this change, that test would start returning the portable ChatGPT process as a Codex process.

Please narrow the matcher before merge, for example by requiring the path to look like a Codex/ChatGPT Desktop Codex package layout such as OpenAI.Codex_*\app\ChatGPT.exe, or another reliable Codex-specific signal, instead of accepting all ChatGPT.exe processes. Also update/add Windows tests for both cases:

• portable Codex package ChatGPT.exe should be detected;
• unrelated portable ChatGPT.exe should not be treated as a Codex process.

The packaged activation restriction to WindowsApps looks reasonable; the blocker is the watcher broadening.