docs: Align CONTRIBUTING.md with develop

Replace main CONTRIBUTING.md with the develop tip content so both branches share one guide.

CONTRIBUTING.md

@@ -1,36 +1,44 @@
 # Contributing
 
-## Pull requests
+## Propose changes
 
-Prefer pull requests against `develop`. The repository default is `master`
-or `main`; `develop` exists for ongoing integration.
+Open a pull request against `develop`. Keep the default branch for releases and
+stable tips; land work on `develop` first.
+
+Point at an existing issue when one fits. Prefer a short issue that states the
+symptom or request before a large PR.
 
 ## Commits
 
-Subject form (kernel-style):
+Subject form:
 
-    area: Imperative summary
+```
+area: Imperative summary
+```
 
-- Imperative mood after the colon (`Add`, `Fix`, `Remove`, …).
-- No trailing period on the subject. Aim for about 75 characters total.
-- Body states the problem and why the change is right.
-- One logical change per commit. Skip the body only when the subject alone
-  is obvious to a reviewer.
+- **Area** is a real package, directory, or subsystem token (`ci:`, `docs:`,
+  Go package name). Not a lone filename.
+- **Imperative** mood: Fix, Add, Remove — not "Fixed" or "This patch…".
+- No trailing period. Aim ≤ ~70–75 characters for the whole subject.
+- Not conventional-commits (`feat:` / `fix:` / `chore:` as types).
 
-## Pull request description
+Body explains **why**. Establish the problem, then say what you are doing.
+One logical change per commit; split fix and cleanup.
 
-- **What** — what changed
-- **Why** — problem and impact
-- **Test** — concrete steps a reviewer can run
+## Pull requests
 
-Do not leave the description as “see commits”.
+Title matches the primary commit subject.
 
-## Issues
+- **What** changed
+- **Why** (problem and impact)
+- **Test** (concrete steps; "CI green" alone is weak)
 
-Gitea closes issues when a bare issue reference appears in merge text.
-Cite leftover issues by full URL. Only close an issue when the merge
-actually finishes that work.
+## Issues and closing
+
+Cite leftover issues by **full URL**. Gitea closes issues when `#N` appears in
+merge text, so do not put `#N` in the merge message unless that issue is actually
+done. Use `Fixes #N` / `Closes #N` only when the leftover work is finished.
 
 ## License
 
-License: see LICENSE if present; otherwise TBD by owner.
+License TBD by owner.