feat(hooks): make template hooks sync.branch aware (bd-8ib)

Update the embedded template hooks (used by bd init) to also check
for sync.branch configuration. This complements the earlier update
to examples/git-hooks/.

Changes:
- templates/hooks/pre-push: Skip uncommitted check when sync.branch set
- templates/hooks/pre-commit: Skip flush/staging when sync.branch set
- Bump version to 0.27.1 for all hooks
- Add sync.branch hooks change to --whats-new

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

cmd/bd/templates/hooks/post-checkout

@@ -1,5 +1,5 @@
 #!/bin/sh
-# bd-hooks-version: 0.27.0
+# bd-hooks-version: 0.27.1
 #
 # bd (beads) post-checkout hook
 #