fix: percent-encode ';' in form values

PveHttpClient.EncodeFormValue encoded &, =, +, space, and % but left ';'
literal. PVE's application/x-www-form-urlencoded parser treats a raw ';'
as a field separator (the historical alternative to '&'), so a value like

    boot=order=scsi0;ide2

was split into 'boot=order=scsi0' plus an empty 'ide2' field, and PVE
rejected the PUT with "ide2: unable to parse drive options". This broke
any multi-device boot order set via Set-PveVmConfig -AdditionalConfig,
and any other value containing ';'.

Encode ';' as %3B. Safe under the existing minimal-encoding policy that
keeps ':' and '!' literal for cluster-join: cluster-join payloads never
contain ';', and PVE url-decodes config form values.

Tracked as F088. Closes #64.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/review/findings.json

@@ -2881,6 +2881,36 @@
         "evidence": "Added PveSession.Timeout (default 100s) and a TimeSpan? override on PveHttpClient. Connect-PveServer exposes -TimeoutSeconds to set the session-default; Send-PveFile and Invoke-PveStorageDownload expose -TimeoutSeconds with a 30-minute implicit default so large uploads/downloads do not trip the 100s HttpClient default. -TimeoutSeconds 0 means Timeout.InfiniteTimeSpan. PveHttpClient.SendAsync now catches the TimeoutException-wrapped TaskCanceledException and rethrows it as PveApiException(RequestTimeout) with the resource path.",
         "verified_by": "dotnet build + dotnet test (passed including new SendAsync_TimeoutFires xUnit test) + Pester (-TimeoutSeconds coverage on all three cmdlets)"
       }
+    },
+    {
+      "id": "F088",
+      "title": "Form values containing ';' are split into bogus fields (boot order breaks Set-PveVmConfig)",
+      "category": "api_contract",
+      "severity": "high",
+      "status": "resolved",
+      "first_detected": "2026-05-22",
+      "github_issue": 64,
+      "files": [
+        "src/PSProxmoxVE.Core/Client/PveHttpClient.cs"
+      ],
+      "description": "PveHttpClient.EncodeFormValue percent-encoded &, =, +, space, and % but not ';'. PVE's application/x-www-form-urlencoded parser treats a raw ';' as a field separator, so a value like boot=order=scsi0;ide2 was split into 'boot=order=scsi0' plus an empty 'ide2' field, which PVE rejected with 'ide2: unable to parse drive options'. Affected any config value containing ';' (boot order, hookscript, some args).",
+      "scan_history": [
+        {
+          "scan_date": "2026-05-22",
+          "local_id": null,
+          "status": "new"
+        },
+        {
+          "scan_date": "2026-05-22",
+          "local_id": null,
+          "status": "fixed"
+        }
+      ],
+      "resolution": {
+        "scan_date": "2026-05-22",
+        "evidence": "Added ';' -> %3B to EncodeFormValue. Safe under the minimal-encoding policy (cluster-join values never contain ';' and PVE url-decodes config form values). Verified the colon/comma minimal-encoding behavior is preserved.",
+        "verified_by": "dotnet build + dotnet test (3 new PveHttpClientFormEncodingTests: semicolon encoded on POST/PUT, comma/colon remain literal)"
+      }
     }
   ]
 }