Add GitAgent Protocol support (agent.yaml + SOUL.md)

[computer-agent]

Hi! 👋 This PR proposes GitAgent Protocol (GAP) support for DM-Code-Agent — an open standard for portable, interoperable AI agents (https://gitagent.sh).

DM-Code-Agent is a great fit for GAP: it has a clear purpose, explicit skills, multi-LLM support, and a strong sense of what it is and isn't. The manifest faithfully represents what the agent already does — nothing invented.

What this adds (two files only, nothing else changes):

• agent.yaml — a standard manifest capturing the agent's name, version, model preferences, 11 discrete skills (ReAct loop, task planner, trace writer, Reflexion, Critic, Self-Consistency, Adaptive Replanning, context memory, MCP integration, skill system, maintenance benchmark), runtime config, and compliance tier.
• SOUL.md — a clean description of the agent's persona, working style, capabilities, and hard constraints — distilled from the README and AGENTS.md.

Why this might be useful:

• With these files, DM-Code-Agent can run on any GAP-compatible runtime without extra glue.
• It can be listed in the Open GAP registry so other developers can discover it.
• The files serve as machine-readable documentation of what the agent does and doesn't do.

Totally fine to tweak, close, or ask questions. Thanks for building something auditable and transparent in the open! 🦀

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⭐ If the standard looks useful, the project lives at https://github.com/open-gitagent/opengap — a star helps more maintainers find it.