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/draftStarters.ts

@@ -27,6 +27,7 @@ export const BUILTIN_STARTERS: readonly BuiltInStarter[] = [
     { name: 'catch-up', icon: 'history', labelKey: 'chat.draftPresets.catchup.label', command: '/catch-up' },
     { name: 'weigh', icon: 'scales-3', labelKey: 'chat.draftPresets.weigh.label', command: '/weigh' },
     { name: 'plan-feature', icon: 'survey', labelKey: 'chat.draftPresets.plan.label', command: '/plan-feature' },
+    { name: 'craft-goal', icon: 'target', labelKey: 'chat.draftPresets.craftGoal.label', command: '/craft-goal' },
     { name: 'debug', icon: 'bug', labelKey: 'chat.draftPresets.debug.label', command: '/debug' },
     { name: 'review', icon: 'search-eye', labelKey: 'chat.draftPresets.review.label', command: '/workspace-review' },
 ];