fix(auth): survive missing OIDC interaction cookie on magic-link click

Clicking the wiki magic-link email was producing SessionNotFound:
'interaction session id cookie not found' from
provider.interactionFinished, because that call requires the short-lived
_interaction cookie to be present on the request. It isn't, when:

- the user clicks the email on a different device or browser
- the interaction cookie already expired
- the user is in private/incognito browsing

Those unhandled errors previously bounced to /coming-soon via the
coming-soon middleware, stranding users on the pre-register page.

Instead of relying on the interaction cookie at the magic-link step:

1. Verify the JWT, look up the member, set the auth-token cookie.
2. Redirect the user back to https://wiki.ghostguild.org.
3. Outline re-initiates OIDC, which creates a fresh interaction whose
   cookie IS present on the same request, and [uid].get.ts SSOs the user
   in via the auth-token cookie we just set.

Also swap the createError throws for sendRedirect to /auth/oidc-error so
token/member/status failures land on the styled error page rather than
Nitro's default unhandled-error response.

server/routes/oidc/interaction/verify.get.ts

@@ -5,19 +5,28 @@
  *
  * This is the endpoint the magic link email points to. It:
  * 1. Verifies the JWT token
- * 2. Sets the Ghost Guild session cookie (so future logins are SSO)
- * 3. Completes the OIDC interaction so the user is redirected back to Outline
+ * 2. Sets the Ghost Guild auth-token cookie
+ * 3. Redirects the user back to the wiki — [uid].get.ts will then SSO them
+ *    into a fresh OIDC interaction using that cookie
+ *
+ * We do NOT call provider.interactionFinished here because it requires the
+ * short-lived _interaction cookie on the request, which is missing when the
+ * user clicks the email link on a different device, in a different browser,
+ * in a private window, or after the interaction cookie expired. That path
+ * throws SessionNotFound, which was leaving users stranded on /coming-soon.
  */
 import jwt from "jsonwebtoken";
 import Member from "../../../models/member.js";
 import { connectDB } from "../../../utils/mongoose.js";
-import { getOidcProvider } from "../../../utils/oidc-provider.js";
+
+const OIDC_ERROR = (description: string) =>
+  `/auth/oidc-error?error=invalid_request&error_description=${encodeURIComponent(description)}`;
 
 export default defineEventHandler(async (event) => {
   const { token } = getQuery(event);
 
   if (!token) {
-    throw createError({ statusCode: 400, statusMessage: "Token is required" });
+    return sendRedirect(event, OIDC_ERROR("Login link is missing its token."), 302);
   }
 
   const config = useRuntimeConfig(event);
@@ -26,29 +35,30 @@ export default defineEventHandler(async (event) => {
   try {
     decoded = jwt.verify(token as string, config.jwtSecret) as typeof decoded;
   } catch {
-    throw createError({
-      statusCode: 401,
-      statusMessage: "Invalid or expired token",
-    });
+    return sendRedirect(
+      event,
+      OIDC_ERROR("This login link is invalid or has expired. Please request a new one."),
+      302
+    );
   }
 
   await connectDB();
   const member = await (Member as any).findById(decoded.memberId);
 
   if (!member) {
-    throw createError({ statusCode: 404, statusMessage: "Member not found" });
+    return sendRedirect(event, OIDC_ERROR("Member not found."), 302);
   }
 
   if (member.status === "suspended" || member.status === "cancelled") {
-    throw createError({
-      statusCode: 403,
-      statusMessage: `Account is ${member.status}`,
-    });
+    return sendRedirect(
+      event,
+      OIDC_ERROR(`Account is ${member.status}.`),
+      302
+    );
   }
 
-  // Set Ghost Guild session cookie for future SSO
   const sessionToken = jwt.sign(
-    { memberId: member._id, email: member.email },
+    { memberId: member._id, email: member.email, tv: member.tokenVersion },
     config.jwtSecret,
     { expiresIn: "7d" }
   );
@@ -57,19 +67,12 @@ export default defineEventHandler(async (event) => {
     httpOnly: true,
     secure: process.env.NODE_ENV === "production",
     sameSite: "lax",
+    path: "/",
     maxAge: 60 * 60 * 24 * 7,
   });
 
-  // Complete the OIDC interaction
-  const provider = await getOidcProvider();
-  const result = {
-    login: { accountId: member._id.toString() },
-  };
-
-  await provider.interactionFinished(
-    event.node.req,
-    event.node.res,
-    result,
-    { mergeWithLastSubmission: false }
-  );
+  // Send the user back to the wiki. Outline will bounce them to /oidc/auth,
+  // which creates a fresh interaction whose cookie WILL be present, and then
+  // [uid].get.ts sees the auth-token we just set and SSOs them through.
+  return sendRedirect(event, "https://wiki.ghostguild.org", 302);
 });