chore: add initial CODEOWNERS

.github/CODEOWNERS

@@ -0,0 +1,23 @@
+# Code owners for this UFS-Chem application repository.
+#
+# Policy (enforced by the repository rulesets, not by this file):
+#   - main:    2 approvals from @ufs-community/chem-core-team
+#   - develop: 1 approval  from @ufs-community/chem-core-team
+#   - Area owners listed below are auto-requested and their review is
+#     expected; the core team may approve on their behalf when they are
+#     unavailable or the change is trivial.
+#
+# Rules for editing this file:
+#   - The last matching pattern wins.
+#   - EVERY line must include @ufs-community/chem-core-team. A line
+#     without it removes the core team as owner of that path and lets an
+#     absent area owner block a merge. A pre-commit hook enforces this.
+#   - Keep the catch-all first and area lines below it, most specific last.
+
+# Catch-all
+*                       @ufs-community/chem-core-team
+
+# Area owners (add as they are established; keep the core team on the line).
+# Owners may be org teams or individual GitHub users; both need write access.
+# /src/process/dust/    @ufs-community/chem-core-team @ufs-community/<area-team>
+# /src/process/seas/    @ufs-community/chem-core-team @<github-username>

.pre-commit-config.yaml

@@ -66,3 +66,15 @@ repos:
                 src/external/yaml-cpp/.*|
                 CHANGELOG.md
             )$
+
+  - repo: local
+    hooks:
+      - id: codeowners-core-team
+        name: CODEOWNERS lines include the core team
+        description: Every non-comment line of .github/CODEOWNERS must list @ufs-community/chem-core-team.
+        language: system
+        files: ^\.github/CODEOWNERS$
+        entry: >-
+          awk '!/^[[:space:]]*(#|$)/ && !/@ufs-community\/chem-core-team/
+          {bad=1; print FILENAME ": line " NR " lacks @ufs-community/chem-core-team: " $0}
+          END {exit bad}'

docs/developer-guide/contributing.md

@@ -77,7 +77,7 @@ When you are ready to submit your contribution, push your branch to your fork an
 
 - **Fill out the template**: Your pull request should include a clear description of the changes you have made and why. Please fill out the pull request template completely.
 - **Pass the checks**: Your pull request will be automatically tested by our continuous integration (CI) system. All checks must pass before your pull request can be merged.
-- **Respond to feedback**: The maintainers will review your pull request and may request changes. Please be responsive to their feedback.
+- **Respond to feedback**: Reviewers and approval requirements are defined in [`.github/CODEOWNERS`](https://github.com/ufs-community/CATChem/blob/develop/.github/CODEOWNERS); the header of that file explains the policy. Reviewers may request changes. Please be responsive to their feedback.
 
 ## Getting Help