Add agent instructions bundle editing

Expose first-class instructions bundle APIs, preserve agent prompt bundles in portability flows, and replace the Agent Detail prompts tab with file-backed bundle editing while retiring bootstrap prompt UI.

Co-Authored-By: Paperclip <noreply@paperclip.ing>

server/src/services/index.ts

@@ -1,6 +1,7 @@
 export { companyService } from "./companies.js";
 export { companySkillService } from "./company-skills.js";
 export { agentService, deduplicateAgentName } from "./agents.js";
+export { agentInstructionsService, syncInstructionsBundleConfigFromFilePath } from "./agent-instructions.js";
 export { assetService } from "./assets.js";
 export { documentService, extractLegacyPlanBody } from "./documents.js";
 export { projectService } from "./projects.js";