feat(ui): add fable tier row in model mapping

tests/unit/shared/extended-context-utils.test.ts

@@ -0,0 +1,24 @@
+import { describe, expect, it } from 'bun:test';
+
+import {
+  ANTHROPIC_MODEL_ENV_KEYS,
+  isAnthropicModelEnvKey,
+} from '../../../src/shared/extended-context-utils';
+
+describe('Anthropic model env keys', () => {
+  it('includes all five tier mapping keys', () => {
+    expect([...ANTHROPIC_MODEL_ENV_KEYS]).toEqual([
+      'ANTHROPIC_MODEL',
+      'ANTHROPIC_DEFAULT_OPUS_MODEL',
+      'ANTHROPIC_DEFAULT_SONNET_MODEL',
+      'ANTHROPIC_DEFAULT_HAIKU_MODEL',
+      'ANTHROPIC_DEFAULT_FABLE_MODEL',
+    ]);
+  });
+
+  it('recognizes the fable tier key like the other tiers', () => {
+    expect(isAnthropicModelEnvKey('ANTHROPIC_DEFAULT_FABLE_MODEL')).toBe(true);
+    expect(isAnthropicModelEnvKey('ANTHROPIC_DEFAULT_HAIKU_MODEL')).toBe(true);
+    expect(isAnthropicModelEnvKey('ANTHROPIC_BASE_URL')).toBe(false);
+  });
+});