docs: add conventional PR title guidance with Linear references

.github/pull_request_template.md

@@ -0,0 +1,30 @@
+<!--
+Use a Conventional Commit PR title: <type>(<optional scope>): <description>
+
+Examples:
+  feat(incidents): add incident filtering [IR-1234]
+  fix(alerts): handle missing alert details [IR-1234]
+  docs: clarify CLI configuration
+  chore(deps): update dependencies
+
+Use feat for new features, fix for bug fixes, and ! before the colon for
+breaking changes, e.g. feat!: remove a deprecated command.
+
+Release Please uses commit messages for release notes and version bumps.
+When squash-merging, ensure the final commit title follows this format too.
+Keep relevant Linear issue IDs as a title suffix, as shown above, and link
+the ticket in the description. The title must start with the Conventional
+Commit type, not the ticket ID (e.g. avoid [IR-1234] feat(...): ...).
+-->
+
+## Description
+
+<!-- What changes are being made, and why? Link any relevant Linear issues. -->
+
+## Testing
+
+<!-- Describe how the changes were verified, or explain why tests are not needed. -->
+
+## Risk Assessment
+
+<!-- Describe any risks, breaking changes, or migration steps. -->