Related to #596
**Problem:**
Users were seeing persistent "permission denied" error messages for VMs
that simply didn't have qemu-guest-agent installed or running. The error
detection logic was too broad and classified Proxmox API 500 errors as
permission issues, even when they indicated guest agent unavailability.
**Root Cause:**
When qemu-guest-agent is not installed or not running, Proxmox API returns
various error responses (500, 403) that may contain permission-related text.
The previous error detection logic checked for "permission denied" strings
without considering the HTTP status code context, leading to:
- VMs with guest agent: guest details display correctly
- VMs without guest agent: false "Permission denied" error shown
**Solution:**
Enhanced error classification logic to distinguish between:
1. Actual permission issues (401/403 with permission keywords)
2. Guest agent unavailability (500 errors)
3. Agent timeout issues
4. Other agent errors
The fix ensures that only explicit authentication/authorization errors
(401 Unauthorized, 403 Forbidden with permission keywords) are classified
as permission-denied, while API 500 errors are correctly identified as
agent-not-running issues.
**Changes:**
- Reordered error detection to check most specific patterns first
- Added HTTP status code context to permission error detection
- 500 errors now correctly map to "agent-not-running" status
- Only 401/403 errors with explicit permission keywords trigger "permission-denied"
- Improved log messages to guide users toward correct resolution
- Fixed err.Error() vs errStr variable inconsistency
**Impact:**
Users will now see accurate error messages that guide them to:
- Install qemu-guest-agent when it's missing (most common case)
- Check permissions only when there's an actual auth/authz issue
- Understand the difference between agent problems and permission problems
f0088070be