docs: add conventional PR title guidance with Linear references

.github/pull_request_template.md

@@ -0,0 +1,36 @@
+<!--
+Use a Conventional Commit PR title: <type>(<optional scope>): <description>
+
+Examples:
+  feat(incidents): add incident search support [PRF-3498]
+  fix(client): preserve configured request timeout [TER-227]
+  docs: clarify SDK 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 client method.
+
+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 [PRF-3498] feat(...): ...).
+-->
+
+## Description
+
+<!-- What changes are being made in this PR? -->
+
+## Motivation
+
+<!-- Why are we making this change? What problem does it solve? Link any related issues. -->
+
+## Testing
+
+- [ ] Added new tests for this functionality
+- [ ] Existing tests cover this change
+- [ ] No tests needed (explain why below)
+
+## Risk Assessment
+
+<!-- Describe the risk level (low/medium/high) and any rollout considerations. -->