Don't trap when two accounts share a sourceKey

Adding the same server and username twice yields two connections with the
same sourceKey. PaginationState.rehydrate built its lookup with
Dictionary(uniqueKeysWithValues:), which traps on a duplicate key, so every
merged overview (notifications, issues/PRs, repositories) crashed on
construction. Keep the first source instead, and add a regression test.

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

Forji/Forji/Helpers/TaggedItem.swift

@@ -73,8 +73,11 @@ extension PaginationState where Item: Identifiable {
     /// Replace placeholder auth services using the given connection sources.
     /// Items whose sourceKey has no matching source are removed.
     func rehydrate<T>(from sources: [ConnectionSource]) where Item == TaggedItem<T> {
+        // Two connected accounts with the same server+username share a sourceKey,
+        // so keep the first rather than trapping on a duplicate key.
         let lookup = Dictionary(
-            uniqueKeysWithValues: sources.map { ($0.sourceKey, $0.authService) },
+            sources.map { ($0.sourceKey, $0.authService) },
+            uniquingKeysWith: { first, _ in first },
         )
         items = items.compactMap { item in
             guard let auth = lookup[item.sourceKey] else { return nil }

Forji/ForjiTests/TaggedItemTests.swift

@@ -190,4 +190,33 @@ struct TaggedItemTests {
 
         #expect(pagination.items.isEmpty)
     }
+
+    @MainActor
+    @Test func rehydrateHandlesDuplicateSourceKeys() {
+        // Two connected accounts with the same server+username produce duplicate
+        // sourceKeys; rehydrate must not trap on the duplicate key.
+        let liveAuth = AuthenticationService()
+        let key = "https://a.com:u"
+        let sources = [
+            ConnectionSource(
+                sourceKey: key, name: "A",
+                client: ForgejoClient(serverURL: "https://a.com", username: "u", token: "t"),
+                authService: liveAuth,
+            ),
+            ConnectionSource(
+                sourceKey: key, name: "A (duplicate)",
+                client: ForgejoClient(serverURL: "https://a.com", username: "u", token: "t"),
+                authService: AuthenticationService(),
+            ),
+        ]
+        let pagination = PaginationState<TaggedItem<FIssue>>()
+        pagination.items = [
+            TaggedItem(item: makeIssue(id: 1), sourceKey: key, instanceName: "A", authService: makeAuth()),
+        ]
+
+        pagination.rehydrate(from: sources)
+
+        #expect(pagination.items.count == 1)
+        #expect(pagination.items[0].authService === liveAuth) // first source wins
+    }
 }