only master agent explains rules and story

[Gawor270]

Closes FCE-2161
Version 1 of user coordination

[Copilot]

Pull Request Overview

This PR implements a dual-agent system where only the first (master) agent explains the game rules and story, while subsequent agents assume players already understand the context.

Key changes:

• Introduced a master agent with full rule explanations for the first session
• Modified non-master agents to skip rule explanations and assume prior knowledge
• Refactored agent creation logic into a dedicated method

Reviewed Changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
deep-sea-stories/packages/backend/src/utils.ts	Added getMasterInstructionsForStory function for master agent instructions
deep-sea-stories/packages/backend/src/service/elevenlabs-session.ts	Refactored agent creation to differentiate between master and regular agents based on session count
deep-sea-stories/packages/backend/src/prompts/master-instructions-template.md	Created new template with full game rules and story setup for master agent
deep-sea-stories/packages/backend/src/prompts/instructions-template.md	Updated to remove initial story reading and assume players know the rules
deep-sea-stories/packages/backend/src/config.ts	Exported new MASTER_AGENT_INSTRUTIONS_TEMPLATE constant

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[linear]

FCE-2161 Coordinate multiple users conversation