fix(exe-dev): skip PEM validation when sshPrivateKey is a saved secret-ref UUID (PAPA-407)

When the operator picks a saved secret in the JsonSchemaForm, the persisted value is
the bare UUID of the secret record, not the PEM. Run-time secret resolution swaps in
the actual key before SSH, but config save-time validation was rejecting the UUID as
an invalid PEM. Skip PEM checks when the value matches the server-side secret-ref
UUID regex.

packages/plugins/sandbox-providers/exe-dev/src/plugin.test.ts

@@ -202,6 +202,26 @@ describe("exe.dev sandbox provider plugin", () => {
       expect(validateSshPrivateKey(VALID_RSA_PEM)).toBeNull();
     });
 
+    it("accepts UUID-like secret reference values from the save-time schema stage", async () => {
+      process.env.EXE_API_KEY = "host-key";
+
+      const result = await plugin.definition.onEnvironmentValidateConfig?.({
+        driverKey: "exe-dev",
+        config: {
+          apiKey: "api-key",
+          sshPrivateKey: "11111111-1111-4111-8111-111111111111",
+        },
+      });
+
+      expect(result).toMatchObject({
+        ok: true,
+        normalizedConfig: {
+          sshPrivateKey: "11111111-1111-4111-8111-111111111111",
+        },
+      });
+      expect(result?.errors ?? []).toEqual([]);
+    });
+
     it("treats empty / whitespace-only input as valid (falls back to on-host key)", () => {
       expect(validateSshPrivateKey("")).toBeNull();
       expect(validateSshPrivateKey("   \n\n  ")).toBeNull();

packages/plugins/sandbox-providers/exe-dev/src/plugin.ts

@@ -69,6 +69,7 @@ const MAX_VM_RECORD_DEPTH = 4;
 const EXE_DEV_SSH_ONBOARDING_MARKER = "Please complete registration by running: ssh exe.dev";
 const EXE_DEV_SSH_EMAIL_PROMPT = "Please enter your email address:";
 const EXE_DEV_SSH_INVALID_KEY_FORMAT = /Load key [^\n]*invalid format/i;
+const UUID_SECRET_REF_RE = /^[0-9a-f]{8}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{4}-[0-9a-f]{12}$/i;
 
 // exe.dev's `--setup-script` runs at VM init as the unprivileged `exedev` user, which
 // has passwordless sudo. The Paperclip sandbox callback bridge is a Node script, so
@@ -140,6 +141,10 @@ function isValidUrl(value: string): boolean {
   }
 }
 
+function isSecretRef(value: string): boolean {
+  return UUID_SECRET_REF_RE.test(value);
+}
+
 // Catch the SSH-key paste failure modes we've seen in the wild (wrong file,
 // PPK export, truncated paste) before the user pays the cost of provisioning a
 // VM and getting a cryptic SSH error. Inline parse — no `ssh-keygen` dependency
@@ -758,7 +763,7 @@ const plugin = definePlugin({
     ) {
       errors.push("strictHostKeyChecking cannot be empty.");
     }
-    if (config.sshPrivateKey) {
+    if (config.sshPrivateKey && !isSecretRef(config.sshPrivateKey)) {
       const sshKeyError = validateSshPrivateKey(config.sshPrivateKey);
       if (sshKeyError) errors.push(sshKeyError);
     }