feat(FN-3006): merge fusion/fn-3006

Commits merged:
- fix(FN-3006): complete Step 3 — repair dashboard typecheck mapper signatures
- test(FN-3006): complete Step 2 — cover Use default reselection flow
- feat(FN-3006): complete Step 1 — resolve default model selection target

Files changed:
.../app/components/ModelOnboardingModal.tsx        | 24 ++++++---
 packages/dashboard/app/components/QuickChatFAB.tsx | 13 +++--
 .../dashboard/app/components/SettingsModal.tsx     | 24 ++++++---
 .../app/components/__tests__/QuickChatFAB.test.tsx | 61 ++++++++++++++++++++++
 4 files changed, 103 insertions(+), 19 deletions(-)

Fusion-Task-Id: FN-3006

packages/dashboard/app/components/ModelOnboardingModal.tsx

@@ -25,14 +25,22 @@ import { LoginInstructions } from "./LoginInstructions";
 import { CustomProviderForm } from "./CustomProviderForm";
 import { appendTokenQuery } from "../auth";
 
-const mapLegacyCustomProviderToConfig = (provider: CustomProvider): CustomProviderConfig => ({
-  id: provider.id,
-  name: provider.name,
-  baseUrl: provider.baseUrl,
-  api: provider.apiType === "anthropic-compatible" ? "anthropic-messages" : "openai-responses",
-  apiKey: provider.apiKey,
-  models: provider.models?.map((model) => ({ id: model.id, name: model.name })) ?? [],
-});
+const mapLegacyCustomProviderToConfig = (
+  provider: CustomProvider | CustomProviderConfig,
+): CustomProviderConfig => {
+  if ("api" in provider) {
+    return provider;
+  }
+
+  return {
+    id: provider.id,
+    name: provider.name,
+    baseUrl: provider.baseUrl,
+    api: provider.apiType === "anthropic-compatible" ? "anthropic-messages" : "openai-responses",
+    apiKey: provider.apiKey,
+    models: provider.models?.map((model) => ({ id: model.id, name: model.name })) ?? [],
+  };
+};
 
 /** Provider-specific API key setup metadata for onboarding form rendering */
 interface ApiKeyInfo {

packages/dashboard/app/components/QuickChatFAB.tsx

@@ -727,6 +727,7 @@ export function QuickChatFAB({
   const [models, setModels] = useState<ModelInfo[]>([]);
   const [modelsLoading, setModelsLoading] = useState(false);
   const [selectedModel, setSelectedModel] = useState<string>("");
+  const [configuredDefaultModelSelection, setConfiguredDefaultModelSelection] = useState<string>("");
   const [messageInput, setMessageInput] = useState("");
   const [mentionFilter, setMentionFilter] = useState("");
   const [mentionPopupVisible, setMentionPopupVisible] = useState(false);
@@ -805,10 +806,12 @@ export function QuickChatFAB({
   const fileInputRef = useRef<HTMLInputElement | null>(null);
   const pendingAttachmentsRef = useRef<PendingAttachment[]>([]);
 
-  const parsedModelSelection = useMemo(() => parseModelSelection(selectedModel), [selectedModel]);
+  const resolvedModelSelection = selectedModel || configuredDefaultModelSelection;
+
+  const parsedModelSelection = useMemo(() => parseModelSelection(resolvedModelSelection), [resolvedModelSelection]);
   const selectedModelInfo = useMemo(
-    () => models.find((model) => `${model.provider}/${model.id}` === selectedModel) ?? null,
-    [models, selectedModel],
+    () => models.find((model) => `${model.provider}/${model.id}` === resolvedModelSelection) ?? null,
+    [models, resolvedModelSelection],
   );
   const selectedModelTag = useMemo(
     () => formatModelTagName(selectedModelInfo, parsedModelSelection),
@@ -870,6 +873,7 @@ export function QuickChatFAB({
             (model) => `${model.provider}/${model.id}` === defaultSelection,
           );
           if (hasDefaultModel) {
+            setConfiguredDefaultModelSelection(defaultSelection);
             setSelectedModel(defaultSelection);
             // Switch to model mode regardless of whether agents are present —
             // a configured default model is an explicit user preference and
@@ -881,6 +885,8 @@ export function QuickChatFAB({
           }
         }
 
+        setConfiguredDefaultModelSelection("");
+
         // Always pre-select the first model so users can start chatting in model mode
         // without having to manually pick from the dropdown.
         const firstModel = loadedModels[0];
@@ -891,6 +897,7 @@ export function QuickChatFAB({
       .catch((error: unknown) => {
         console.error("[QuickChatFAB] Failed to load models:", error);
         setModels([]);
+        setConfiguredDefaultModelSelection("");
       })
       .finally(() => {
         setModelsLoading(false);

packages/dashboard/app/components/SettingsModal.tsx

@@ -46,14 +46,22 @@ const GITHUB_STAR_CACHE_KEY = "fusion_github_star_count";
 const GITHUB_STAR_CACHE_TTL_MS = 60 * 60 * 1000; // 1 hour
 const GITHUB_STAR_CLICKED_KEY = "fusion:github-star-clicked";
 
-const mapLegacyCustomProviderToConfig = (provider: CustomProvider): CustomProviderConfig => ({
-  id: provider.id,
-  name: provider.name,
-  baseUrl: provider.baseUrl,
-  api: provider.apiType === "anthropic-compatible" ? "anthropic-messages" : "openai-responses",
-  apiKey: provider.apiKey,
-  models: provider.models?.map((model) => ({ id: model.id, name: model.name })) ?? [],
-});
+const mapLegacyCustomProviderToConfig = (
+  provider: CustomProvider | CustomProviderConfig,
+): CustomProviderConfig => {
+  if ("api" in provider) {
+    return provider;
+  }
+
+  return {
+    id: provider.id,
+    name: provider.name,
+    baseUrl: provider.baseUrl,
+    api: provider.apiType === "anthropic-compatible" ? "anthropic-messages" : "openai-responses",
+    apiKey: provider.apiKey,
+    models: provider.models?.map((model) => ({ id: model.id, name: model.name })) ?? [],
+  };
+};
 
 function getNodeStatusLabel(status: "online" | "offline" | "connecting" | "error"): string {
   if (status === "online") return "Online";

packages/dashboard/app/components/__tests__/QuickChatFAB.test.tsx

@@ -298,6 +298,67 @@ describe("QuickChatFAB", () => {
     });
   });
 
+  it("reselecting Use default resolves to configured default model and keeps send enabled", async () => {
+    mockAgentsHook([]);
+    mockFetchModels.mockResolvedValue({
+      models: mockModels,
+      favoriteProviders: [],
+      favoriteModels: [],
+      defaultProvider: "openai",
+      defaultModelId: "gpt-4o",
+    });
+
+    render(<QuickChatFAB addToast={addToast} projectId="proj-123" />);
+    fireEvent.click(screen.getByTestId("quick-chat-fab"));
+
+    await waitFor(() => {
+      expect(screen.getByTestId("quick-chat-model-tag")).toHaveTextContent("GPT-4o");
+      expect(screen.getByTestId("quick-chat-input")).not.toBeDisabled();
+    });
+
+    await selectModelOption("Claude Sonnet 4.5");
+    await waitFor(() => {
+      expect(screen.getByTestId("quick-chat-model-tag")).toHaveTextContent("Claude Sonnet 4.5");
+      expect(mockCreateChatSession).toHaveBeenCalledWith(
+        {
+          agentId: "__fn_agent__",
+          modelProvider: "anthropic",
+          modelId: "claude-sonnet-4-5",
+        },
+        "proj-123",
+      );
+    });
+
+    await selectModelOption("Use default");
+
+    await waitFor(() => {
+      expect(screen.getByTestId("quick-chat-model-tag")).toHaveTextContent("GPT-4o");
+      expect(screen.getByTestId("quick-chat-input")).not.toBeDisabled();
+      expect(mockCreateChatSession).toHaveBeenCalledWith(
+        {
+          agentId: "__fn_agent__",
+          modelProvider: "openai",
+          modelId: "gpt-4o",
+        },
+        "proj-123",
+      );
+    });
+
+    const input = screen.getByTestId("quick-chat-input");
+    fireEvent.change(input, { target: { value: "use default still sends" } });
+    fireEvent.click(screen.getByTestId("quick-chat-send"));
+
+    await waitFor(() => {
+      expect(mockStreamChatResponse).toHaveBeenCalledWith(
+        "session-001",
+        "use default still sends",
+        expect.any(Object),
+        [],
+        "proj-123",
+      );
+    });
+  });
+
   it("preserves existing behavior when no default model is configured and agents exist", async () => {
     mockAgentsHook(mockAgents);
     mockFetchModels.mockResolvedValue({