Windows: installed Codex/Claude ACP runtimes are reported as CLI missing

## Problem

On Windows, Buzz Desktop reports Codex and Claude Code as CLI missing / Not installed, although the CLIs and ACP adapters are installed and runnable from a terminal.

Environment observed:

- Codex CLI is available through the OpenAI WindowsApps installation. The resolved command is an extensionless codex alias under %LOCALAPPDATA%\Microsoft\WindowsApps\ or the packaged Codex resources directory.
- Codex ACP adapter: @agentclientprotocol/codex-acp@1.6.2, installed as the npm shim codex-acp.cmd.
- Claude Code CLI: claude.
- Claude ACP adapter: @agentclientprotocol/claude-agent-acp@0.70.0, installed as the npm shim claude-agent-acp.cmd.
- The same commands resolve from a terminal, but the packaged Buzz Desktop process does not report them as installed.

This appears to be a Windows discovery/environment compatibility issue rather than a missing installation. GUI-launched applications can have a different or stale environment from a terminal, and Windows App Execution Aliases may be extensionless.

## Suggested fix

I prepared a small, focused branch with these changes:

1. Include the user npm directory (%APPDATA%\npm\), WindowsApps, and other relevant Windows locations in discovery.
2. Fall back to paths derived from the home directory when APPDATA / LOCALAPPDATA are unavailable.
3. Rebuild the common path list dynamically instead of caching it for the entire process lifetime.
4. Probe extensionless Windows aliases in addition to .exe, .cmd, and .bat.
5. Add Windows regression coverage for the WindowsApps path and extensionless command candidates.

I have not yet been able to run the Rust build/tests locally because the Rust toolchain is not installed in this development environment. TypeScript checks and git diff --check pass.

I would be grateful if the maintainers could review whether this diagnosis matches the intended discovery behavior and decide whether some or all of the changes are appropriate for upstream. I am happy to adjust the patch based on feedback.

## Reproduction

1. Install Codex CLI through the Windows desktop/App Execution Alias and install the ACP adapter with npm.
2. Install Claude Code and @agentclientprotocol/claude-agent-acp with npm.
3. Launch Buzz Desktop from the installed application rather than from a terminal.
4. Open Settings → Agents and run discovery.
5. Observe Codex/Claude Code reported as missing despite the commands being available in a terminal.

Commit prepared locally: cc5147514 (DCO signed).