test(dashboard): restore the missing api mock export in ResearchView tests (#3239)

## What

Partial fix for **red main**. Test-only.

`ResearchView.test.tsx` has **4 failing tests on main**; 2 fail with:

```
No "fetchBoardWorkflows" export is defined on the "../../api" mock
```

The `vi.mock("../../api")` factory **replaces the whole module**, so
every import anywhere in the rendered tree must appear in it.
`fetchBoardWorkflows` reached this file *indirectly* — the task modals
ResearchView opens import it — so adding that export to product code
broke four cases that have nothing to do with board workflows.

Stubbed with the flag-OFF payload the server sends when multi-lane
boards are disabled, which is the shape these cases already assume.

## Measured

```
before: Tests 4 failed | 23 passed (27)
after:  Tests 2 failed | 25 passed (27)
lint clean; fnxc-future-dates: none added
```

## The remaining 2 are a different cause and are NOT fixed here

They fail with `Number of calls: 0` — the enrich-task and create-task
actions never fire. That is a UI-wiring question, not mock completeness.

**I checked that my stub is not responsible**, rather than assuming:
re-running with `flagEnabled: true` and a populated workflow list
produces the *same* 2 failures, so the payload shape does not gate those
affordances. Left for whoever owns that surface.

## How this was found

While establishing a clean baseline for the resolver audit. That sweep
also reported `lazy-loaded-views-docs.test.ts` red — **it now passes**,
fixed by another worker between my measurement and this PR, which is why
the count here is 3 files rather than the 4 I reported in #3236.

Still red on main, untouched by this PR:
- `src/__tests__/planning-browser-e2e.test.ts` — `expected {
totalButtons: 1, …(7) } to match object { totalButtons: 1, …(6) }`; an
assertion shape gained a field.
- `src/__tests__/register-model-routes-kimi-k3-supplemental.test.ts` —
`Test timed out in 15000ms`. Per the standing rule a timeout with no
corresponding bug in the change is a **quarantine candidate**, not
something to appease with a longer timeout; I am not quarantining it
unilaterally since it is not my subsystem, but flagging it as the shape
that rule describes.

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

@@ -29,6 +29,24 @@ vi.mock("../../api", () => ({
   fetchSettings: (...args: unknown[]) => mockFetchSettings(...args),
   fetchAuthStatus: (...args: unknown[]) => mockFetchAuthStatus(...args),
   fetchTasks: (...args: unknown[]) => mockFetchTasks(...args),
+  /*
+  FNXC:ResearchViewTests 2026-07-31-20:24:
+  This factory REPLACES the whole `../../api` module, so every import anywhere in the rendered tree
+  must appear here or it resolves to undefined. `fetchBoardWorkflows` reached this file indirectly —
+  the task modals ResearchView opens import it — and its absence failed four cases with
+  `No "fetchBoardWorkflows" export is defined on the "../../api" mock`, none of which are about board
+  workflows.
+
+  Returns the flag-OFF payload the server sends when multi-lane boards are disabled, which is the
+  shape these cases already assume: no board metadata, legacy rendering, and the consumers'
+  `.then()` handlers take their empty-state path rather than a fabricated workflow list.
+  */
+  fetchBoardWorkflows: vi.fn().mockResolvedValue({
+    flagEnabled: false,
+    defaultWorkflowId: "",
+    workflows: [],
+    taskWorkflowIds: {},
+  }),
 }));
 
 vi.mock("lucide-react", async (importOriginal) => {