feat: expand magic prompts coverage and split generation prompts (#835)

- Add configurable visible/instructions prompt families for commit/PR generation, PR checks/comments flows, and git conflict resolution helpers.
- Refactor prompt sending to explicit visible + synthetic parts instead of newline-based splitting, with legacy override migration for old keys.
- Polish Magic Prompts settings UX with grouped sidebar entries, tooltip-based descriptions, AI icon, and validation that visible prompts cannot be empty across web and VS Code runtimes.

packages/ui/src/lib/settings/metadata.ts

@@ -16,6 +16,7 @@ export type SettingsPageSlug =
   | 'chat'
   | 'shortcuts'
   | 'sessions'
+  | 'magic-prompts'
   | 'notifications'
   | 'voice'
   | 'tunnel';
@@ -167,6 +168,13 @@ export const SETTINGS_PAGE_METADATA: readonly SettingsPageMeta[] = [
     kind: 'single',
     keywords: ['defaults', 'default agent', 'default model', 'retention', 'memory', 'limits', 'zen'],
   },
+  {
+    slug: 'magic-prompts',
+    title: 'Magic Prompts',
+    group: 'general',
+    kind: 'split',
+    keywords: ['prompts', 'templates', 'git', 'github', 'review', 'commit', 'pull request'],
+  },
 
   { slug: 'notifications', title: 'Notifications', group: 'general', kind: 'single', keywords: ['alerts', 'native', 'summary', 'summarization'], },
   { slug: 'voice', title: 'Voice', group: 'advanced', kind: 'single', keywords: ['tts', 'speech', 'voice'], isAvailable: (ctx) => !ctx.isVSCode },