[meta-darwin][PATCH] Add AGENTS.md for AI agent conventions

[ecordonnier@snap.com]

From: Etienne Cordonnier <ecordonnier@snap.com>

Aligned with openembedded-core AGENTS.md; mailing list details match README.

AI-Generated: Composer 2.5
Signed-off-by: Etienne Cordonnier <ecordonnier@snap.com>
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+# AGENTS.md — meta-darwin
+
+Guidance for AI agents working in the `meta-darwin` repository.
+
+## Making changes
+
+- No web PR workflow. The project use **patches on mailing lists**
+  (yocto-patches@lists.yoctoproject.org; use `[meta-darwin]` in the subject, see README). Don't
+  assume GitHub PR conventions apply.
+- One Git commit per logical change (e.g., one commit per recipe added/upgraded).
+- Commit message format:
+  - Summary line prefixed with the recipe name or short file path,
+    e.g. `openssl: upgrade 3.2.0 -> 3.2.1` or `classes/rootfs-postcommands: fix typo`.
+    Check `git log --oneline <path>` for the prefix convention already in use.
+  - Body explains what/why/how, and how it was tested.
+  - Prefer explaining *why* a change was made over restating what's
+    already visible in the diff, unless the diff is long/hard to follow
+    or the reason for the change isn't known — in those cases, summarize
+    what changed instead.
+  - Be succinct: use as few sentences and lines as possible while still
+    covering what/why/how. Cut restatements, filler, and any detail a
+    reviewer wouldn't need (e.g. exact test-run counts, step-by-step
+    narration). One short paragraph is usually enough; only add a second
+    if a distinct point (e.g. testing) needs it.
+  - The most relevant information about the change should be presented first.
+  - Reference bugs as `[YOCTO #1234]` when applicable.
+  - Use `Reported-by`, `Suggested-by`, `Tested-by`, `Reviewed-by`, `Cc` tags
+    where relevant.
+
+### AI-generated code
+
+- **Mandatory**: any AI-generated code/commit must add an `AI-Generated:`
+  tag line in the commit message, placed *before* `Signed-off-by` (if present),
+  naming the tool used, e.g.:
+
+  ```
+  component: Add the ability to ...
+
+  AI-Generated: Uses GitHub Copilot
+  ```
+
+- Also add a code comment or other in-patch indication that the code is
+  AI-generated (recommended, not just the commit tag).
+- **Mandatory** Do not automatically add a `Signed-off-by`. This tag must
+  always be written by the human contributor, never by the AI tool — the
+  DCO/Developer's Statement of Origin still applies in full.
+- Contributor is responsible for confirming the AI tool's terms don't
+  conflict with the project's open source license/IP policy, and that
+  any third-party copyrighted material in the AI output is properly
+  licensed before contributing it. See the Linux Foundation generative AI
+  guidance: https://www.linuxfoundation.org/legal/generative-ai.
+- `Co-authored-by` should be omitted in favor of the `AI-generated` tag.
+
+When in doubt about a convention, grep `git log --oneline <path>` in the
+target repo for precedent before inventing a new style.
-- 
2.43.0