feat: enable system prompt inject from mcp server based classifier

[rootfs]

What type of PR is this?

Followup #368 to support system prompt injection for each category.

What this PR does / why we need it:

Which issue(s) this PR fixes:

Fixes #

Release Notes: Yes/No

[github-actions]

👥 vLLM Semantic Team Notification

The following members have been identified for the changed files in this PR and have been automatically assigned:

📁 config

Owners: @rootfs
Files changed:

• config/config-mcp-classifier-example.yaml

📁 Root Directory

Owners: @rootfs, @Xunzhuo
Files changed:

• examples/mcp-classifier-server/README.md
• examples/mcp-classifier-server/server.py

📁 src

Owners: @rootfs, @Xunzhuo, @wangchen615
Files changed:

• src/semantic-router/pkg/connectivity/mcp/api/types.go
• src/semantic-router/pkg/utils/classification/classifier.go
• src/semantic-router/pkg/utils/classification/mapping.go
• src/semantic-router/pkg/utils/classification/mcp_classifier.go
• src/semantic-router/pkg/utils/classification/mcp_classifier_test.go

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🎉 Thanks for your contributions!

This comment was automatically generated based on the OWNER files in the repository.

[Copilot]

Pull Request Overview

This PR extends the MCP classifier functionality to support per-category system prompts and descriptions. It enables MCP servers to provide specialized system prompts for each category that the router can inject when processing queries, allowing for domain-specific LLM behavior.

Key changes:

• Added support for storing and retrieving per-category system prompts and descriptions from MCP servers
• Enhanced the CategoryMapping and Classifier structs with new methods to access category-specific metadata
• Updated the MCP server example to demonstrate per-category system prompt usage

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/semantic-router/pkg/utils/classification/mcp_classifier_test.go	Added comprehensive tests for per-category system prompt functionality
src/semantic-router/pkg/utils/classification/mcp_classifier.go	Updated to store category system prompts and descriptions from MCP response
src/semantic-router/pkg/utils/classification/mapping.go	Added fields and methods for category system prompts and descriptions
src/semantic-router/pkg/utils/classification/classifier.go	Added public methods to retrieve category system prompts and descriptions
src/semantic-router/pkg/connectivity/mcp/api/types.go	Extended ListCategoriesResponse with system prompts and descriptions fields
examples/mcp-classifier-server/server.py	Enhanced to provide per-category system prompts and descriptions
examples/mcp-classifier-server/README.md	Updated documentation to explain per-category system prompt usage
config/config-mcp-classifier-example.yaml	Added extensive comments explaining the new functionality

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[Copilot]

Pull Request Overview

Copilot reviewed 8 out of 8 changed files in this pull request and generated no new comments.

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[wangchen615]

LGTM