feat: landing redesign in resources aesthetic; fix KB search crash

Landing:
- Rebuilt app/(landing)/page.tsx from a 539-line client monolith to a
  ~150-line server component in the /resources editorial style.
- New scoped app/(landing)/landing.css mirrors the resources palette
  (#0c0c0c / lime #d4ff00 / #252525), IBM Plex Mono + Libre
  Baskerville loaded in (landing)/layout.tsx, faint grid overlay.
- Removed the animated Mini* previews and inline Ico* set (clashed
  with the editorial look). Split into components/landing/icons.tsx
  and components/landing/resource-showcase.tsx for separation.
- Resource showcase: one row of six square tiles with the real
  project SVG logos linking to atlas/space-after-dark/proposal-duel/
  zine/learner/governance. Responsive 6 -> 3 -> 2.
- BrandMark accepts an optional style prop.

Fix:
- KB search crashed the Ops page. filteredLeads referenced
  l.member_name (the column is lead_handle), so undefined.toLowerCase()
  threw on every keystroke since the filter memos recompute on shared
  search state across tabs. All Ops filter predicates are now
  null-safe via a shared has() helper; filteredSecrets no longer
  assumes a non-null title.

Docs:
- docs/PERMISSIONS_DESIGN.md: concrete plan for customizable
  permissions, per-item Ops ACLs, and area-lead roles. That work is
  security-sensitive (RLS rewrites on secrets/knowledge_base) and is
  scoped as its own next pass, not bundled here.

266/266 tests pass. Production build clean. No migration this pass.

components/landing/resource-showcase.tsx

@@ -0,0 +1,43 @@
+import Link from 'next/link'
+import { AtlasLogo } from '@/components/resources/atlas-logo'
+import { CubeIcon, TraceIcon, SpaceIcon, GridIcon, KeyIcon } from '@/components/resources/icons'
+
+// The six hackerspace.sh research/game projects, shown as a single row of
+// square tiles at the foot of the landing page. Internal routes use next/link;
+// the interactive learner is an external app.
+const RESOURCES = [
+  { title: 'Atlas', href: '/atlas', external: false, visual: <AtlasLogo /> },
+  { title: 'Space After Dark', href: '/space-after-dark', external: false, visual: <CubeIcon /> },
+  { title: 'Proposal Duel', href: '/proposal-duel', external: false, visual: <TraceIcon /> },
+  { title: 'The Hackerspace Game', href: '/zine', external: false, visual: <SpaceIcon /> },
+  { title: 'Interactive Learner', href: 'https://hackerspacegame.netlify.app/', external: true, visual: <GridIcon /> },
+  { title: 'Governance in a Box', href: '/governance', external: false, visual: <KeyIcon /> },
+]
+
+export function ResourceShowcase() {
+  return (
+    <section className="landing-section">
+      <div className="landing-container">
+        <div className="landing-section-head">
+          <span className="landing-section-label">From hackerspace.sh</span>
+          <span className="landing-section-note">06 projects</span>
+        </div>
+        <div className="landing-showcase">
+          {RESOURCES.map(r =>
+            r.external ? (
+              <a key={r.title} href={r.href} target="_blank" rel="noopener noreferrer" className="landing-tile">
+                <span className="landing-tile-visual">{r.visual}</span>
+                <span className="landing-tile-title">{r.title}</span>
+              </a>
+            ) : (
+              <Link key={r.title} href={r.href} className="landing-tile">
+                <span className="landing-tile-visual">{r.visual}</span>
+                <span className="landing-tile-title">{r.title}</span>
+              </Link>
+            ),
+          )}
+        </div>
+      </div>
+    </section>
+  )
+}