fix: add version marker to post-checkout hook and include in CheckGitHooks

The post-checkout hook was missing the bd-hooks-version marker that the other
hooks have, and it wasn't being checked by CheckGitHooks(). This caused
version mismatch issues during hook status checks.

Changes:
- Added 'bd-hooks-version: 0.23.1' marker to post-checkout hook
- Updated CheckGitHooks() to include post-checkout in the list of hooks to check

This ensures all four git hooks (pre-commit, post-merge, pre-push, post-checkout)
have consistent version tracking.

Fixes bd-kb4g

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

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

cmd/bd/hooks.go

@@ -42,7 +42,7 @@ type HookStatus struct {
 
 // CheckGitHooks checks the status of bd git hooks in .git/hooks/
 func CheckGitHooks() ([]HookStatus, error) {
-	hooks := []string{"pre-commit", "post-merge", "pre-push"}
+	hooks := []string{"pre-commit", "post-merge", "pre-push", "post-checkout"}
 	statuses := make([]HookStatus, 0, len(hooks))
 
 	for _, hookName := range hooks {

cmd/bd/templates/hooks/post-checkout

@@ -1,4 +1,5 @@
 #!/usr/bin/env bash
+# bd-hooks-version: 0.23.1
 #
 # Beads post-checkout hook
 # Automatically imports JSONL to SQLite database after checking out branches