docs: add tag release workflow to AGENTS.md

AGENTS.md

@@ -105,6 +105,45 @@ Implement CRC8-CCITT (poly 0x07) for CRSF frame validation.
 Added unit tests for empty, single-byte, and known-value cases.
 ```
 
+## Tag Releases
+
+Use annotated tags for releases. Write the release notes to a temporary
+file, then use it as the tag message. Do **not** commit the release
+notes file.
+
+Write release notes:
+```sh
+cat > RELEASES.md << 'EOF'
+# Releases
+
+## 0.1.0 (2026-06-15)
+
+Initial release. Windows-only support.
+
+### Library (`celrs`)
+
+- **CRSF protocol** ...
+EOF
+```
+
+Create the annotated tag:
+```sh
+git tag -a v0.1.0 -F RELEASES.md
+```
+
+Verify:
+```sh
+git show v0.1.0
+```
+
+Remove the temporary file:
+```sh
+rm RELEASES.md
+```
+
+Release notes follow the same Markdown rules as `AGENTS.md` (80-column
+wrap, no em dashes, etc.). Version format is `v<major>.<minor>.<patch>`.
+
 ## Documentation (Markdown)
 
 - Wrap normal text and lists at **max 80 columns** (for readability in