feat: add cherry-pick-sync skill (#385)

* feat: add cherry-pick-sync skill for main→release branch syncing
* fix: address PR review feedback on cherry-pick-sync skill

Author: amilz

.claude/skills/cherry-pick-sync/SKILL.md

@@ -0,0 +1,132 @@
+---
+name: cherry-pick-sync
+description: >-
+  Sync commits from main to the active release/* branch via cherry-pick PR.
+  Use when the user says "sync main to release", "cherry-pick to release",
+  "sync release branch", "backport to release", "keep release up to date",
+  or wants to ensure hotfixes/patches on main are reflected in the release branch.
+  Also use when the user asks to "cherry-pick commits" between branches.
+---
+
+# Cherry-Pick Sync: Main to Release Branch
+
+Cherry-pick commits from `main` into the active `release/*` branch and create a PR.
+Resolve conflicts automatically when safe; ask the user when ambiguous.
+
+## Workflow
+
+### 1. Identify the release branch
+
+```bash
+# Prefer: open PRs from release/* branches (shows active work)
+gh pr list --state open --head "release/" --json headRefName --jq '.[].headRefName' 2>/dev/null
+
+# Fallback: most recent remote release branch by commit date
+git branch -r --sort=-committerdate | grep 'origin/release/' | head -5
+```
+
+- One active `release/*` branch → use it.
+- Multiple → ask the user; suggest the most recently committed as the default.
+- User specified one → use that.
+
+### 2. Determine commits to cherry-pick
+
+```bash
+git fetch origin main <release-branch>
+git log --oneline --reverse origin/<release-branch>..origin/main
+```
+
+**Filtering rules:**
+- User specified commits (SHAs/keywords) → use only those.
+- User said to skip certain commits → exclude them.
+- Default → take ALL commits from the log above.
+- **Auto-skip** release-only commits: version bumps, CHANGELOG updates, "chore: release v*". Flag these as skipped with reason.
+- Show the final commit list to the user and confirm before proceeding.
+
+### 3. Check preconditions
+
+```bash
+# Must have clean working directory
+git status --porcelain
+```
+
+If dirty, ask the user to commit or stash first.
+
+### 4. Create working branch
+
+Replace `/` with `-` in the release branch name when constructing the working branch:
+
+```bash
+git checkout -b chore/cherry-pick-main-into-$(echo <release-branch> | tr '/' '-')-YYYYMMDD origin/<release-branch>
+```
+
+Example: `release/2.2.0` → `chore/cherry-pick-main-into-release-2.2.0-20260313`.
+
+### 5. Cherry-pick commits
+
+Cherry-pick one at a time to isolate conflicts:
+
+```bash
+git cherry-pick <sha>
+```
+
+**On conflict:**
+1. Inspect the conflict markers.
+2. **Auto-resolve** if obvious and low-risk: import ordering, trivial merge context, whitespace.
+3. **Ask the user** if: logic changes, behavioral differences, unclear intent, or risk of breaking something.
+4. After resolving: `git add .` then `git cherry-pick --continue`.
+5. If a commit cannot be applied and user agrees → `git cherry-pick --skip`.
+
+Track all skipped and conflict-resolved commits for the PR body.
+
+**Abort/rollback:** If the user wants to cancel the entire operation:
+```bash
+git cherry-pick --abort
+git checkout -
+git branch -D <working-branch>
+```
+Inform the user the repo has been restored to its original state.
+
+**Already applied:** If cherry-pick says "already applied" or produces an empty commit, skip silently.
+
+### 6. Push and create PR
+
+```bash
+git push -u origin HEAD
+
+gh pr create \
+  --base <release-branch> \
+  --title "chore: sync main into <release-branch> (YYYY-MM-DD)" \
+  --body "<see template below>"
+```
+
+**PR body template:**
+
+```markdown
+## Summary
+
+Cherry-pick commits from `main` into `<release-branch>` to keep the release branch in sync with hotfixes and patches.
+
+### Commits included
+
+- `abc1234` fix: description (#123)
+- `def5678` feat: description (#456)
+
+### Commits skipped
+
+- `ghi9012` chore: release v2.0.5 (release-only)
+- _None_ (if empty)
+
+### Conflicts resolved
+
+- `path/to/file.rs`: brief explanation of resolution
+- _None_ (if empty)
+```
+
+### 7. Return the PR URL
+
+## Edge Cases
+
+- **No new commits** → tell user branches are in sync. Do not create empty PR.
+- **User on wrong branch** → always create working branch from `origin/<release-branch>` regardless of current branch.
+- **Multiple release branches** → ask which one; suggest the most recently committed as default.