refactor: remove main session key references and enhance agent-gateway associations

frontend/src/components/gateways/GatewayForm.tsx

@@ -9,7 +9,6 @@ type GatewayFormProps = {
   name: string;
   gatewayUrl: string;
   gatewayToken: string;
-  mainSessionKey: string | null;
   workspaceRoot: string;
   gatewayUrlError: string | null;
   gatewayCheckStatus: GatewayCheckStatus;
@@ -34,7 +33,6 @@ export function GatewayForm({
   name,
   gatewayUrl,
   gatewayToken,
-  mainSessionKey,
   workspaceRoot,
   gatewayUrlError,
   gatewayCheckStatus,
@@ -130,28 +128,16 @@ export function GatewayForm({
         </div>
       </div>
 
-      <div className="grid gap-6 md:grid-cols-2">
-        <div className="space-y-2">
-          <label className="text-sm font-medium text-slate-900">
-            Main session key (read-only)
-          </label>
-          <Input
-            value={mainSessionKey ?? "Auto-generated by server"}
-            readOnly
-            disabled
-          />
-        </div>
-        <div className="space-y-2">
-          <label className="text-sm font-medium text-slate-900">
-            Workspace root <span className="text-red-500">*</span>
-          </label>
-          <Input
-            value={workspaceRoot}
-            onChange={(event) => onWorkspaceRootChange(event.target.value)}
-            placeholder={workspaceRootPlaceholder}
-            disabled={isLoading}
-          />
-        </div>
+      <div className="space-y-2">
+        <label className="text-sm font-medium text-slate-900">
+          Workspace root <span className="text-red-500">*</span>
+        </label>
+        <Input
+          value={workspaceRoot}
+          onChange={(event) => onWorkspaceRootChange(event.target.value)}
+          placeholder={workspaceRootPlaceholder}
+          disabled={isLoading}
+        />
       </div>
 
       {errorMessage ? (