[Enhancement]: Add Full MCP Prompts Support

[vincent-herlemont]

What features would you like to see added?

Full support for MCP prompts as defined in the Model Context Protocol specification.

Currently, LibreChat has no usable MCP prompts support:

• prompts/list exists in code but is only used internally for connection health checks, not exposed to users
• prompts/get is not implemented
• notifications/prompts/list_changed is not implemented
• No API endpoints for prompts
• No UI to browse or use prompts

More details

The code has fetchPrompts() in packages/api/src/mcp/connection.ts but it's never called for user-facing features. It's only used as a fallback to verify if a connection is alive.

MCP prompts allow servers to provide reusable message templates. For example, a server could offer a "code_review" prompt that takes code as input and returns a structured review request.

To fully support MCP prompts:

1. Expose prompts/list results to users (API + UI)
2. Implement prompts/get to fetch prompt content with arguments
3. Handle notifications/prompts/list_changed to update UI when prompts change

Reference: https://modelcontextprotocol.io/specification/2025-06-18/server/prompts

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This feature needs new UI components. Some questions to consider:

• How should users discover and browse available MCP prompts?
• Should prompts appear as slash commands (like /code_review) in the chat input?
• How to handle prompt arguments? A form? Inline input?
• Should there be a dedicated prompts panel or integrate into the existing MCP tools UI?
• How to display prompts from multiple MCP servers?

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What do you think of this feature? Could you help me, I'm willing to propose an implementation.

Which components are impacted by your request?

General

Pictures

No response

Code of Conduct

• I agree to follow this project's Code of Conduct

Related PR: #9991