Fix inverted cancel guard in cockpit project loader

Why: #102 rewrote the bare-array fallback into a multi-line callback and
turned 'if (!c) setProjects(...)' into an early 'if (!c) return', which
skips setProjects on the normal (non-cancelled) path — the cockpit then
hangs on 加载中 forever, caught by I4 e2e scenario 1.

Evidence: tsc clean, vitest 324/324, build green (SELF); seven-scenario
browser suite rerun recorded on the Dev I4 card.

Impact: cockpit entry only.

Refs: rollout I4

src/components/DocumentCockpit.tsx

@@ -66,7 +66,7 @@ export function DocumentCockpit() {
     setProjects(null); setPid(''); setOverview(null); setSelected(null); setFilter(''); setError('')
     api.rdmCommand<{ projects?: ProjectView[] } | ProjectView[]>('rdm.project.list')
       .then(list => {
-        if (!c) return
+        if (c) return
         // rdm.project.list 返回 { projects: [...] }；容忍裸数组形态。
         const rows = Array.isArray(list) ? list : (list?.projects ?? [])
         setProjects(rows)