ci: keep backport PR titles conventional

[harshtandiya]

Problem

backport.yml set:

pull_title: '[Backport ${target_branch}] ${pull_title}'

The prefix pushes the conventional-commit type out of first position, so amannn/action-semantic-pull-request in PR Title Check cannot parse it. Every generated backport PR failed the check and needed a manual retitle.

Fix

• pull_title: '${pull_title}' — reuse the source title verbatim. It is already conventional (the source PR passed the same check).
• add_labels: backport — the label carries the "this is a backport" signal that the title prefix used to. The backport label already exists in this repo.

This matches upstream frappe, which uses title: "{{originalTitle}}" plus labelsToAdd: "backport".

Notes

• backport (no space) does not match label_pattern: '^backport ([^ ]+)$', so labelling the generated PR cannot re-trigger the workflow.
• Target branch is still visible in the PR body (Automated backport of #N to \branch``) and in the generated branch name.

🤖 Generated with Claude Code

[greptile-apps]

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[github-actions]

Backport failed for main, because it was unable to cherry-pick the commit(s).

Please cherry-pick the changes locally and resolve any conflicts.

git fetch origin main
git worktree add -d .worktree/backport-291-to-main origin/main
cd .worktree/backport-291-to-main
git switch --create backport-291-to-main
git cherry-pick -x 7094813c5cb097476272069d6b308ac7f89ff863