Add backport-email skill

Author: steveisok

.github/skills/backport-email/SKILL.md

@@ -0,0 +1,81 @@
+---
+name: backport-email
+description: Generate a backport email from a PR for sending to Tactics. Use when asked to create or generate a backport email.
+---
+
+# Backport Email Generation
+
+Generate a formatted email for requesting backport approval from Tactics.
+
+## Required Input
+
+Ask the user for the **backport PR URL** if not provided. Example:
+- `https://github.com/dotnet/runtime/pull/124058`
+
+## Process
+
+1. **Fetch the backport PR** using the GitHub MCP tools to get:
+   - PR number and title
+   - Target release branch (e.g., `release/9.0`)
+   - PR description containing the servicing template sections
+
+2. **Extract from the PR description:**
+   - Link to the original main PR
+   - Link to the issue being fixed
+   - DESCRIPTION section
+   - CUSTOMER IMPACT section (including checkboxes)
+   - REGRESSION section (including checkboxes)
+   - TESTING section
+   - RISK section
+
+3. **Generate the email** following the template at `.github/BACKPORT_EMAIL_TEMPLATE.md`
+
+## Output Format
+
+Output the email as **plain text** (not markdown) since email clients don't render markdown.
+
+```
+Subject: [release/X.0] Backport request: <TITLE> (#<PR_NUMBER>)
+
+Hello Tactics,
+
+Please consider https://github.com/dotnet/runtime/pull/<PR_NUMBER> for backporting into release/X.0.
+
+Fixes https://github.com/dotnet/runtime/issues/<ISSUE_NUMBER>
+
+main PR: <MAIN_PR_LINK>
+
+**DESCRIPTION**
+
+<description text>
+
+**CUSTOMER IMPACT**
+
+- [ ] Customer reported
+- [ ] Found internally
+
+<customer impact text>
+
+**REGRESSION**
+
+- [ ] Yes
+- [ ] No
+
+<regression text>
+
+**TESTING**
+
+<testing text>
+
+**RISK**
+
+<risk text>
+```
+
+## Important Notes
+
+- **Do NOT attempt to open the email in Outlook or any email client.** Just output the formatted text for the user to copy.
+- Preserve the `**bold**` section headers as they appear reasonably well in plain-text emails.
+- Preserve the checkbox format `- [ ]` or `- [x]` from the PR description.
+- Extract the release branch version (e.g., `9.0`) from the PR's base branch.
+- If any section is missing from the PR description, note it and leave a placeholder.