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

cmd/bd/templates/hooks/post-merge

@@ -0,0 +1,42 @@
+#!/bin/sh
+# bd-hooks-version: 0.22.1
+#
+# bd (beads) post-merge hook
+#
+# This hook syncs the bd database after a git pull or merge:
+# 1. Checks if any .beads/*.jsonl file was updated
+# 2. Runs 'bd sync --import-only' to import changes
+#
+# Installation:
+#   cp examples/git-hooks/post-merge .git/hooks/post-merge
+#   chmod +x .git/hooks/post-merge
+#
+# Or use the install script:
+#   examples/git-hooks/install.sh
+
+# Check if bd is available
+if ! command -v bd >/dev/null 2>&1; then
+    echo "Warning: bd command not found, skipping post-merge sync" >&2
+    exit 0
+fi
+
+# Check if we're in a bd workspace
+if [ ! -d .beads ]; then
+    # Not a bd workspace, nothing to do
+    exit 0
+fi
+
+# Check if any JSONL file exists in .beads/
+if ! ls .beads/*.jsonl >/dev/null 2>&1; then
+    exit 0
+fi
+
+# Run bd sync --import-only to import the updated JSONL
+# This is more robust than direct import as it handles all edge cases
+if ! bd sync --import-only >/dev/null 2>&1; then
+    echo "Warning: Failed to sync bd changes after merge" >&2
+    echo "Run 'bd sync --import-only' manually" >&2
+    # Don't fail the merge, just warn
+fi
+
+exit 0