docs: scope AGENTS instructions by directory (#2083)

.github/AGENTS.md

@@ -0,0 +1,30 @@
+# GitHub Workflow Instructions
+
+Applies to `.github/` and repository pull-request operations.
+
+## Pull Requests
+
+- PR titles and descriptions must be in English.
+- Use `.github/pull_request_template.md` for every PR body.
+- Keep all template section headings.
+- Use `N/A` for non-applicable sections.
+- Include verification commands in the PR details.
+- For `gh pr create` and `gh pr edit`, always write markdown body to a file and pass `--body-file`.
+- Do not use multiline inline `--body`; backticks and shell expansion can corrupt content or trigger unintended commands.
+- Recommended pattern:
+  - `cat > /tmp/pr_body.md <<'EOF'`
+  - `...markdown...`
+  - `EOF`
+  - `gh pr create ... --body-file /tmp/pr_body.md`
+
+## CI Alignment
+
+When changing CI-sensitive behavior, keep local validation aligned with `.github/workflows/ci.yml`.
+
+Current `test-and-lint` gate includes:
+
+- `cargo nextest run --all --exclude e2e_test`
+- `cargo test --all --doc`
+- `cargo fmt --all --check`
+- `cargo clippy --all-targets --all-features -- -D warnings`
+- `./scripts/check_layer_dependencies.sh`