fix(tests): clear the persisted Command Center sub-tab between cases (7 of 8 main reds) (#2971)

`main` is red in the dashboard backfill lane. This fixes **7 of the 8**
failures. All 8 bisect to #2420 (`4f929acc10`): parent `189f237a07`
passes 9/9, that commit fails 5.

### Cause — test-order pollution, not a product bug

#2420 made Command Center restore its sub-tab on remount, because the
view unmounts on navigation by design:

```ts
const [activeTab, setActiveTab] = useState<SubViewId>(
  () => (getCommandCenterState(projectId)?.activeTab as SubViewId | undefined) ?? "overview",
);
```

The panel's test id is derived from that tab
(`data-testid={\`command-center-panel-${activeTab}\`}`), and these files
click through to other tabs — `tokens`, `team`, `github`, `system`,
`mission-control`. Neither `beforeEach` cleared storage, so the
**first** case left `mission-control` persisted and every later case
rendered `command-center-panel-mission-control`:

```
→ Unable to find an element by: [data-testid="command-center-panel-overview"]
```

Nothing in that message points at a previous test, which is what made it
look like a component regression.

**Confirmed as ordering rather than breakage:** each failing case passes
when run alone with `-t`. The "mutation" here is `main` itself — without
the `localStorage.clear()` these files fail 7; with it, 11/11.

### Scope

Two lines plus the note explaining why they exist, so the next person
who adds a tab-switching case knows the persistence is per-project and
sticky. **No product code touched** — the persistence behaviour in #2420
is correct and stays as-is.

**Verified:** 11/11 across both files, `tsc -p tsconfig.app.json` 0
errors, lint clean, FNXC gate exit 0. Test-only, no changeset.

### The 8th failure is NOT fixed here, deliberately

`MainContent.planning-project-remount.test.tsx` fails because #2420
moved Planning out of `MainContent` (its branch now returns `null`) into
`PlanningKeepAlive`, mounted by `App.tsx`. The product side is right —
the host **is** keyed (`App.tsx:1956`):

```jsx
<PlanningKeepAlive key={`${currentProject.id}:${modalManager.planningEntryGeneration}`} … />
```

so project switches still remount and I found **no cross-project leak**.
But that test was `FNXC:ProjectSwitchModalReset` coverage for a
leak-class invariant (Planning carrying a previous project's
stream/session), and **nothing asserts it at the new location**: the
keep-alive test covers navigation reveal, not project switching, and
`App.test.tsx` has no test for the host key. Deleting that `key=` today
would fail no test.

Restoring it needs an App-level test, which is a bigger change than this
fix and worth keeping separate. Detailed on #2420.

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

packages/dashboard/app/components/command-center/__tests__/CommandCenter.mobile-scroll.test.tsx

@@ -368,6 +368,20 @@ async function openChartTab(tab: string) {
 
 describe("CommandCenter mobile scroll regression (FN-6595)", () => {
   beforeEach(() => {
+  /*
+  FNXC:CommandCenter 2026-07-30-22:10:
+  CLEAR THE PERSISTED SUB-TAB — cases in this file are no longer independent without it.
+
+  #2420 made `activeTab` initialise from per-project persisted state
+  (`getCommandCenterState(projectId)?.activeTab`) instead of always `"overview"`, because Command
+  Center unmounts on navigation by design and has to restore its sub-tab on remount. These cases
+  click through to other tabs, so the FIRST case now leaves `mission-control` persisted and every
+  later case renders `command-center-panel-mission-control` — the `command-center-panel-overview`
+  lookups then fail with no hint that the cause is a previous test.
+
+  Confirmed as ordering, not breakage: each failing case passes when run alone with `-t`.
+  */
+  localStorage.clear();
     apiMock.mockReset();
     mockOverviewApi();
     injectCommandCenterCss();

packages/dashboard/app/components/command-center/__tests__/CommandCenter.tablet-layout.test.tsx

@@ -391,6 +391,20 @@ async function openChartTab(tab: string) {
 
 describe("CommandCenter tablet layout regression (FN-6679)", () => {
   beforeEach(() => {
+  /*
+  FNXC:CommandCenter 2026-07-30-22:10:
+  CLEAR THE PERSISTED SUB-TAB — cases in this file are no longer independent without it.
+
+  #2420 made `activeTab` initialise from per-project persisted state
+  (`getCommandCenterState(projectId)?.activeTab`) instead of always `"overview"`, because Command
+  Center unmounts on navigation by design and has to restore its sub-tab on remount. These cases
+  click through to other tabs, so the FIRST case now leaves `mission-control` persisted and every
+  later case renders `command-center-panel-mission-control` — the `command-center-panel-overview`
+  lookups then fail with no hint that the cause is a previous test.
+
+  Confirmed as ordering, not breakage: each failing case passes when run alone with `-t`.
+  */
+  localStorage.clear();
     apiMock.mockReset();
     mockOverviewApi();
     injectCommandCenterCss();