Add bd hooks install command with embedded git hooks (bd-908z)

- Embed git hooks in binary using go:embed and templates directory
- Add bd hooks install/uninstall/list subcommands
- Install hooks with automatic backup of existing hooks
- Update AGENTS.md to reference 'bd hooks install' instead of install.sh
- Add comprehensive tests for hooks commands
- Update hook version to 0.22.1

Closes bd-908z

examples/git-hooks/pre-push

@@ -1,5 +1,5 @@
 #!/bin/sh
-# bd-hooks-version: 0.22.0
+# bd-hooks-version: 0.22.1
 #
 # bd (beads) pre-push hook
 #