feat: add sync-git skill and script

Add a Claude Code skill and bash script to sync the local repo
with upstream, prune stale remote-tracking refs, and delete
local branches already merged into main.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: LeeCampbell

.claude/skills/sync-git/SKILL.md

@@ -0,0 +1,8 @@
+---
+name: sync-git
+description: Sync local repo with upstream, clean up branches and remotes
+disable-model-invocation: true
+allowed-tools: Bash
+---
+
+Run `bash scripts/synch-git.sh` and report the output to the user.

scripts/synch-git.sh

@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+echo "=== Syncing main with upstream ==="
+git fetch upstream main
+git checkout main
+git merge upstream/main --ff-only
+
+echo ""
+echo "=== Pruning stale remote-tracking references ==="
+git fetch origin --prune
+git fetch upstream --prune
+
+echo ""
+echo "=== Deleting local branches merged into main ==="
+merged=$(git branch --merged main | grep -v '^\*\|main' || true)
+if [ -n "$merged" ]; then
+  echo "$merged" | xargs git branch -d
+else
+  echo "No merged branches to delete."
+fi
+
+echo ""
+echo "=== Done ==="
+git branch