Add issue-first contribution guardrails (#353)

.github/PULL_REQUEST_TEMPLATE.md

@@ -1,3 +1,12 @@
+## Before opening
+
+This repo is issue-first for outside contributions. If you are not `pbakaus` or `abdulwahabone`, please link the issue where a maintainer approved or requested this PR. Unsolicited PRs may be closed without review.
+
+- Linked issue:
+- Contributor status:
+  - [ ] I am `pbakaus` or `abdulwahabone`
+  - [ ] A maintainer approved this PR in the linked issue
+
 ## Summary
 
 <!-- What does this PR change and why? -->
@@ -19,3 +28,5 @@
 - [ ] `bun test` passes
 - [ ] Tested with at least one provider (Cursor / Claude Code / Gemini CLI / Codex / Copilot / Kiro / OpenCode / Qoder)
 - [ ] README / DEVELOP.md updated if needed
+- [ ] I reviewed the full diff myself before requesting human review
+- [ ] I disclosed any AI assistance in this PR and related commits/comments, or no AI assistance was used