agents: add an initial agents.md

Set out some high level rules for all agent code contributions.

Signed-off-by: Liam Girdwood <liam.r.girdwood@linux.intel.com>

Author: lrgirdwo

AGENTS.md

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+# Sound Open Firmware (SOF) Agent Workflows and Rules
+
+This document outlines the rules AI agents must follow when checking out branches, writing code, documenting features, and running the development environment. Follow these rules carefully:
+
+## Development Standards
+
+### Commitment and Sign-off Rules
+* **Commit Subject:** Must follow the format `feature: descriptive title`.
+* **Commit Body:** Should describe the changes in detail in the commit message body.
+* **Sign-off:** All commits must be signed off by the developer (`Signed-off-by: Name <email>`) using the identity from the local git config.
+
+### Documentation Requirements
+* **Doxygen Comments:** Any new C code or features must include Doxygen comments.
+* **Documentation Builds:** Integration of new code must not introduce any new Doxygen errors or warnings. Code additions should be verified against a clean documentation build.
+* **Architectural Consistency:** When adding or updating a file, any `architecture.md` or `README.md` in the same directory must be reviewed. The agent is responsible for ensuring documentation stays in sync with code logic changes.
+
+### Codestyle and Linting
+* **Standard:** Use `clangd` instead of `checkpatch` for codestyle verification.
+* **Rationale:** `checkpatch` is prone to confusion with assembly and non-standard C; `clangd` provides better integration with IDEs and AI tools and is easier to maintain.