Feat/load external mcps

[shehab299]

No description provided.

[Copilot]

Pull request overview

This PR extends the MCP proxy configuration and agent MCP initialization to support loading user-defined (“external”) MCP servers from an on-disk config file, including the ability to disable configured servers and to substitute environment variables in configured env values.

Changes:

• Add disabled support to MCP server entries and filter disabled servers during config parsing.
• Add $VAR / ${VAR} environment-variable substitution for env values in command-based MCP server configs.
• In agent mode, auto-load external MCP servers from the discovered MCP proxy config file (with reserved-name protection), and expose the config discovery helper for reuse.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 3 comments.

File	Description
libs/mcp/proxy/src/client/mod.rs	Adds disabled flag support, env-var substitution for command env vars, and tests for these behaviors.
cli/src/commands/mcp/mod.rs	Makes find_mcp_proxy_config_file public so other CLI modules can reuse config discovery.
cli/src/commands/agent/run/mcp_init.rs	Loads external MCP servers into the proxy config during agent initialization (skipping reserved server names).

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