Add cherry-pick kilocode skill (#42660)

## Summary
- Adds a new kilocode skill for cherry-picking PRs onto release
candidate branches
- Codifies the single-session constraint to prevent duplicate PRs
- Documents branch naming, commit message format, and common issues

## Test plan
- [ ] Verify the skill is picked up by Kilo when prompted with a
cherry-pick task
- [ ] Confirm the documented steps match the existing cherry-pick
workflow

.kilocode/skills/cherry-pick/SKILL.md

@@ -0,0 +1,92 @@
+---
+name: cherry-pick
+description: Cherry-pick a merged PR onto a release candidate branch and open a new PR. Use when asked to cherry-pick, backport, or port a PR to an rc-minor or rc-patch branch.
+---
+
+# Cherry-pick – kilocode skill
+
+## Important: single session only
+
+**Use only a single agent session for the entire cherry-pick.** Multiple sessions for the same cherry-pick have caused duplicate PRs in the past.
+
+## Arguments
+
+This skill expects two arguments:
+
+1. **Target branch** — the release candidate branch (e.g., `rc-minor-fleet-v4.83.0`, `rc-patch-fleet-v4.82.1`)
+2. **Source PR** — a GitHub PR URL or number from the `fleetdm/fleet` repo
+
+## Steps
+
+1. **Fetch the latest remote state**
+
+   ```bash
+   git fetch origin
+   ```
+
+2. **Identify the merge commit** — find the merge commit SHA for the source PR on `main`.
+
+   ```bash
+   gh pr view <PR> --json mergeCommit --jq '.mergeCommit.oid'
+   ```
+
+3. **Create a working branch** from the target release branch:
+
+   ```bash
+   git checkout -b cherry-pick-<PR_NUMBER>-to-<target-branch> origin/<target-branch>
+   ```
+
+4. **Cherry-pick the merge commit** using `-m 1` (mainline parent):
+
+   ```bash
+   git cherry-pick -m 1 <merge-commit-sha>
+   ```
+
+   - If there are conflicts, resolve them and continue the cherry-pick.
+   - If the PR was a squash-merge (single commit, no merge commit), omit `-m 1`.
+
+5. **Push and open a PR** against the target branch:
+
+   ```bash
+   git push -u origin HEAD
+   gh pr create \
+     --base <target-branch> \
+     --title "Cherry-pick #<PR_NUMBER> onto <target-branch>" \
+     --body "Cherry-pick of https://github.com/fleetdm/fleet/pull/<PR_NUMBER> onto the <target-branch> release branch."
+   ```
+
+## Commit message format
+
+Follow the established pattern:
+
+```
+Cherry-pick #<PR_NUMBER> onto <target-branch>
+
+Cherry-pick of https://github.com/fleetdm/fleet/pull/<PR_NUMBER> onto the
+<target-branch> release branch.
+```
+
+If the original commit has a `Co-authored-by` trailer, preserve it.
+
+## Branch naming
+
+```
+cherry-pick-<PR_NUMBER>-to-<target-branch>
+```
+
+Example: `cherry-pick-41914-to-rc-minor-fleet-v4.83.0`
+
+## Common issues
+
+- **Duplicate PRs** — never run multiple agent sessions for the same cherry-pick.
+- **Conflict on cherry-pick** — resolve conflicts manually, then `git cherry-pick --continue`.
+- **Migration timestamp ordering** — if the cherry-picked PR includes migrations, verify timestamps are in chronological order on the target branch.
+
+## References
+
+- Release process: https://github.com/fleetdm/fleet/blob/main/docs/Contributing/workflows/releasing-fleet.md
+- Backport checker: `tools/release/backport-check.sh`
+
+---
+
+*This file will grow as new patterns and constraints are established.*