fix(wsl): add a PowerShell fallback for notifications

[Copilot]

Some WSL environments disable Windows PATH injection, which makes powershell.exe unavailable even though Windows interop is still enabled. In that case, PowerShell notifications stop working because the driver only probes the command by name.

• Binary resolution

  • keep powershell.exe as the default on Windows and WSL
  • when running inside WSL, fall back to /mnt/c/Windows/System32/WindowsPowerShell/v1.0/powershell.exe if powershell.exe is not resolvable from PATH

• Driver behavior

  • isolate binary lookup behind small helper methods so the WSL-specific resolution path is explicit and testable
  • preserve current behavior when powershell.exe is already available

• Coverage

  • add focused tests for:
    • WSL + powershell.exe available → keep default binary
    • WSL + powershell.exe missing + absolute Windows path available → use fallback

• Documentation

  • document the WSL fallback in the driver reference

if ($this->isRunningInsideWsl()
    && !$this->isBinaryAvailableForCommand(self::BINARY)
    && $this->isBinaryAvailableForCommand(self::WSL_FALLBACK_BINARY)
) {
    return self::WSL_FALLBACK_BINARY;
}

[pyrech]

LGTM, thanks

[pyrech]

@copilot Can you squash your commits, please?

[Copilot]

@copilot Can you squash your commits, please?

I can’t rewrite/squash existing commits from this agent environment because force-push is not available here. If you want a single commit on the PR branch, please squash locally or use the repository UI at merge time.