[Enhancement]Improve Skill module to work alongside MCP tools in the agent loop

Description

Problem

The current Skill system runs as a separate pipeline from the main agent loop. When a skill is matched, do_skill() short-circuits the run loop and returns immediately — MCP tools are never invoked. This leads to several related issues:

• Skills and MCP tools are mutually exclusive within a single task
• Skills are only evaluated on the first conversation round (round == 0)
• Skill results are not passed into subsequent tool-calling steps
• No streaming output during skill execution

Direction

Unify skills with the tool-calling mechanism — expose skill operations (skill_list, skill_view, skill_execute) as standard tools via ToolBase, so they coexist with MCP tools in the same step() loop. Inject skill summaries into the system prompt for discoverability.

Status

Analysis complete. Design under discussion — feedback welcome.