feat: add craft-goal session starter and command

Adds /craft-goal autocomplete and chat handling for starting a Goal crafting session.
Introduces new Magic Prompts content and localized labels/descriptions for Goal crafting.
Migrates desktop draft starters to include Craft a Goal once and persists the migration marker.

packages/ui/src/lib/persistence.test.ts

@@ -205,6 +205,7 @@ describe('updateDesktopSettings', () => {
       recentModels: [{ providerID: 'google', modelID: 'gemini-pro' }],
       recentAgents: ['build', 'plan'],
       recentEfforts: { 'anthropic/claude-haiku-4': ['high', 'default'] },
+      draftStartersCraftGoalAdded: true,
     } satisfies SettingsPayload;
     registerSettingsApi(async () => ({}), async () => ({ settings, source: 'web' }));
 
@@ -243,6 +244,7 @@ describe('updateDesktopSettings', () => {
 
       expect(saveCalls).toHaveLength(1);
       expect(saveCalls[0]).toEqual({
+        draftStartersCraftGoalAdded: true,
         favoriteModels: [{ providerID: 'anthropic', modelID: 'claude-haiku-4' }],
         hiddenModels: [{ providerID: 'openai', modelID: 'gpt-5' }],
         collapsedModelProviders: ['openai'],