feat(rah-light): remove unused prompts.ts type file

- Delete src/types/prompts.ts (was used by deleted contextBuilder.ts)
- All other type files verified in use: analytics.ts, database.ts, logs.ts, views.ts, pdf-parse.d.ts

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/types/prompts.ts

@@ -1,25 +0,0 @@
-/**
- * Types for Anthropic prompt caching
- * https://docs.claude.com/en/docs/build-with-claude/prompt-caching
- */
-
-export type CacheControl = { type: 'ephemeral' };
-
-export interface CacheableBlock {
-  type: 'text';
-  text: string;
-  cache_control?: CacheControl;
-}
-
-export interface SystemPromptResult {
-  blocks: CacheableBlock[];
-  cacheHit: boolean;
-}
-
-export interface CacheStats {
-  cacheCreationInputTokens: number;
-  cacheReadInputTokens: number;
-  inputTokens: number;
-  outputTokens: number;
-  savingsPercentage: number;
-}