docs(prompts): add reusable issue-from-branch prompt template

Author: arturcic

.github/prompts/create-issue-from-branch.prompt.md

@@ -0,0 +1,103 @@
+# Create Issue From Branch Changes
+
+Create or update a GitHub issue from the changes in the current branch compared to main.
+
+## Requirements
+
+1. Compare changes from origin/main..HEAD and infer the user-facing goal.
+2. Do not include implementation details (no file lists, refactor notes, internal mechanics).
+3. Ask before editing the issue:
+   - Which label should be used?
+   - Which milestone should be used?
+4. Defaults:
+   - If label is not provided, use improvement.
+   - If milestone is not provided, use the latest open milestone.
+5. The issue description must be well-formatted Markdown.
+6. Use this Markdown structure exactly (omit empty sections):
+   - ## Summary
+   - ## Goal
+   - ## Success Criteria
+   - ## References
+7. Keep language concise, goal-oriented, and user-facing.
+
+## Operational Steps
+
+1. Ensure branch comparison is up to date:
+
+```bash
+git fetch origin main --quiet
+git log --oneline --no-merges origin/main..HEAD
+git diff --name-status origin/main..HEAD
+```
+
+2. Ask:
+   - Label? (default: improvement)
+   - Milestone? (default: latest open milestone)
+
+3. Resolve defaults:
+
+```bash
+LABEL="${LABEL:-improvement}"
+
+if [ -z "$MILESTONE" ]; then
+  MILESTONE="$(gh api repos/{owner}/{repo}/milestones --paginate -f state=open --jq 'sort_by(.number) | last | .title')"
+fi
+```
+
+4. Build a well-formatted Markdown body in a temp file:
+
+```bash
+cat > /tmp/issue-body.md <<'EOF'
+## Summary
+<goal-focused summary>
+
+## Goal
+<what outcome we want>
+
+## Success Criteria
+- <criterion 1>
+- <criterion 2>
+
+## References
+- <optional links>
+EOF
+```
+
+5. Suggest a title in this style:
+   - [IMPROVEMENT]: <goal-focused title>
+   - Adapt prefix to selected label where appropriate (for example: [FEATURE]: ...).
+
+6. Create or update issue:
+
+Create:
+
+```bash
+gh issue create \
+  --title "<TITLE>" \
+  --label "$LABEL" \
+  --milestone "$MILESTONE" \
+  --body-file /tmp/issue-body.md
+```
+
+Update existing:
+
+```bash
+gh issue edit <ISSUE_NUMBER> \
+  --title "<TITLE>" \
+  --add-label "$LABEL" \
+  --milestone "$MILESTONE" \
+  --body-file /tmp/issue-body.md
+```
+
+7. Verify and report final state:
+
+```bash
+gh issue view <ISSUE_NUMBER> --json number,title,url,labels,milestone,body
+```
+
+Report:
+- Issue number and URL
+- Final title
+- Final label(s)
+- Final milestone
+- Confirmation that body is well-formatted Markdown and goal-focused