fix(proxmox): DestroyLXC DELETE takes no body + force=1 (live restore-test teardown)

The slice-6 restore-test teardown failed live: DELETE /lxc/{vmid} with a form body
returns HTTP 501 'Unexpected content for method DELETE', and a booted scratch needs
force=1. Move purge/destroy-unreferenced-disks/force to the query string, send no body.
Regression test locks the contract.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

internal/proxmox/backup_test.go

@@ -0,0 +1,63 @@
+package proxmox
+
+import (
+	"context"
+	"io"
+	"net/http"
+	"strings"
+	"testing"
+)
+
+// TestDestroyLXC_DeleteContract locks the DELETE wire contract: no request body (a form
+// body → PVE HTTP 501 "Unexpected content for method 'DELETE'"), flags in the query string,
+// force=1 so a still-running scratch can be torn down. Regression guard for the slice-6
+// teardown bug.
+func TestDestroyLXC_DeleteContract(t *testing.T) {
+	var gotMethod, gotURL string
+	var gotBody string
+	m := &mockDoer{fn: func(r *http.Request) (*http.Response, error) {
+		gotMethod = r.Method
+		gotURL = r.URL.String()
+		if r.Body != nil {
+			b, _ := io.ReadAll(r.Body)
+			gotBody = string(b)
+		}
+		return jsonResp(200, `{"data":"UPID:demo:0000:vzdestroy::root@pam:"}`), nil
+	}}
+	c := newTestClient(m)
+	upid, err := c.DestroyLXC(context.Background(), 990000)
+	if err != nil {
+		t.Fatalf("DestroyLXC: %v", err)
+	}
+	if upid == "" {
+		t.Error("expected a UPID")
+	}
+	if gotMethod != http.MethodDelete {
+		t.Errorf("method = %s, want DELETE", gotMethod)
+	}
+	if gotBody != "" {
+		t.Errorf("DELETE must send NO body, got %q", gotBody)
+	}
+	for _, want := range []string{"/nodes/demo-felhom/lxc/990000", "purge=1", "destroy-unreferenced-disks=1", "force=1"} {
+		if !strings.Contains(gotURL, want) {
+			t.Errorf("URL %q missing %q", gotURL, want)
+		}
+	}
+}
+
+// TestVzdump_NotesTemplate confirms the notes-template param is sent when set.
+func TestVzdump_NotesTemplate(t *testing.T) {
+	var gotBody string
+	m := &mockDoer{fn: func(r *http.Request) (*http.Response, error) {
+		b, _ := io.ReadAll(r.Body)
+		gotBody = string(b)
+		return jsonResp(200, `{"data":"UPID:demo:0:vzdump::root@pam:"}`), nil
+	}}
+	c := newTestClient(m)
+	if _, err := c.Vzdump(context.Background(), VzdumpOptions{VMID: 9001, Storage: "local", Mode: ModeSnapshot, Notes: "felhom {{guestname}}"}); err != nil {
+		t.Fatal(err)
+	}
+	if !strings.Contains(gotBody, "notes-template=") {
+		t.Errorf("vzdump body missing notes-template: %q", gotBody)
+	}
+}

internal/proxmox/mutate.go

@@ -96,11 +96,12 @@ func (c *Client) DestroyLXC(ctx context.Context, vmid int) (string, error) {
 	if vmid == 0 {
 		return "", fmt.Errorf("proxmox: DestroyLXC needs a vmid")
 	}
-	v := url.Values{}
-	v.Set("purge", "1")
-	v.Set("destroy-unreferenced-disks", "1")
-	path := fmt.Sprintf("/nodes/%s/lxc/%d", c.node, vmid)
-	return c.dataString(ctx, http.MethodDelete, path, v)
+	// DELETE takes NO request body on PVE (a form body → HTTP 501 "Unexpected content for
+	// method 'DELETE'"); the flags go in the query string. `force=1` destroys even a running
+	// guest (the scratch may still be booted at teardown), `purge=1` drops it from jobs/HA,
+	// `destroy-unreferenced-disks=1` reaps orphaned volumes.
+	path := fmt.Sprintf("/nodes/%s/lxc/%d?purge=1&destroy-unreferenced-disks=1&force=1", c.node, vmid)
+	return c.dataString(ctx, http.MethodDelete, path, nil)
 }
 
 // Snapshot creates an LXC snapshot via POST /nodes/{node}/lxc/{vmid}/snapshot.