refactor: rename swift → cortex in code and documentation

Complete rename of "swift" terminology to "cortex" across the codebase:

Code Changes:
- Rename directories: lib/swift → lib/cortex, components/swift → components/cortex
- Rename API routes: /api/swift/* → /api/cortex/*
- Rename page routes: /epd/swift → /epd/cortex
- Rename store: swift-store.ts → cortex-store.ts

Type Renames:
- SwiftIntent → CortexIntent
- SwiftStore → CortexStore
- useSwiftStore → useCortexStore
- SwiftContext → CortexContext
- useSwiftVoice → useCortexVoice

Documentation Updates (docs/intent/):
- Safety Net → Nudge (Layer 3 rename)
- SafetySuggestion → NudgeSuggestion
- evaluateSafetyNet → evaluateNudge
- SWIFT_* feature flags → CORTEX_*
- All path references updated to match new structure

Files affected: 47 files, ~700 lines changed

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

components/cortex/artifacts/artifact-area.tsx

@@ -0,0 +1,30 @@
+'use client';
+
+/**
+ * Artifact Area (v3.0 + E4)
+ *
+ * Displays artifacts using ArtifactContainer with tab support.
+ * Manages multiple artifacts with lifecycle actions.
+ *
+ * Epic: E1 (Foundation), E3 (Chat API), E4 (Artifact Area & Tabs)
+ * Stories: E1.S3, E3.S6, E4.S1, E4.S2
+ */
+
+import { useCortexStore } from '@/stores/cortex-store';
+import { ArtifactContainer } from './artifact-container';
+
+export function ArtifactArea() {
+  const openArtifacts = useCortexStore((s) => s.openArtifacts);
+  const activeArtifactId = useCortexStore((s) => s.activeArtifactId);
+  const switchArtifact = useCortexStore((s) => s.switchArtifact);
+  const closeArtifact = useCortexStore((s) => s.closeArtifact);
+
+  return (
+    <ArtifactContainer
+      artifacts={openArtifacts}
+      activeArtifactId={activeArtifactId}
+      onSelectArtifact={switchArtifact}
+      onCloseArtifact={closeArtifact}
+    />
+  );
+}