refactor: extract LLM system prompt from profile-content to dedicated module

Move the ~110-line LLM system prompt to src/data/llm-prompt.ts, removing
the LLMCopy type, getLLMCopy() accessor, and llm field from ProfileContent.
llm.ts now imports the prompt directly. profile-content.ts drops from 246
to 133 lines, retaining only UI copy and search metadata.

src/lib/llm.ts

@@ -1,4 +1,4 @@
-import { getLLMCopy } from '@/lib/profile-content'
+import { LLM_SYSTEM_PROMPT } from '@/data/llm-prompt'
 
 export interface ChatMessage {
   role: 'user' | 'assistant'
@@ -19,7 +19,7 @@ export function isLLMAvailable(): boolean {
 }
 
 export function buildSystemPrompt(): string {
-  return getLLMCopy().systemPrompt
+  return LLM_SYSTEM_PROMPT
 }
 
 function buildRequestBody(

src/lib/profile-content.ts

@@ -5,7 +5,6 @@ import type {
   EducationCopyEntry,
   ExperienceEducationUICopy,
   LatestResultsCopy,
-  LLMCopy,
   ProfileContent,
   QuickActionCopyEntry,
   SidebarCopy,
@@ -52,7 +51,4 @@ export function getEducationEntries(): ReadonlyArray<EducationCopyEntry> {
   return profileContent.experienceEducation.educationEntries
 }
 
-export function getLLMCopy(): DeepReadonly<LLMCopy> {
-  return profileContent.searchChat.llm
-}