Install portable agent-neutral Hop skill and documentation

Hop-State: A_06FN69X2VW0BAXG4A4DT6V0
Hop-Proposal: R_06FN69VET1STZNKPWK913K8
Hop-Task: T_06FN637799RW5Q7WH9H6PJR
Hop-Attempt: AT_06FN63779BJRBK1VFQ94GRR

scripts/install.ps1

@@ -73,11 +73,14 @@ try {
 
     if (-not $SkipSkill) {
         & $installedBinary skill install --force
+        if ($LASTEXITCODE -ne 0) {
+            throw "Hop skill installation failed with exit code $LASTEXITCODE"
+        }
     }
     Write-Host "Installed $(& $installedBinary version)"
     Write-Host "Binary: $installedBinary"
     if (-not $SkipSkill) {
-        Write-Host "Restart Codex if it is open, then use it normally in any Git repository."
+        Write-Host "Restart any open agent application, then use it normally in any Git repository."
     }
 } finally {
     Remove-Item -Recurse -Force -ErrorAction SilentlyContinue $tempDir