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/pre-push

@@ -0,0 +1,62 @@
+#!/bin/sh
+# bd-hooks-version: 0.22.1
+#
+# bd (beads) pre-push hook
+#
+# This hook prevents pushing stale JSONL by:
+# 1. Flushing any pending in-memory changes to JSONL (if bd available)
+# 2. Checking for uncommitted changes (staged, unstaged, untracked, deleted)
+# 3. Failing the push with clear instructions if changes found
+#
+# The pre-commit hook already exports changes, but this catches:
+# - Changes made between commit and push
+# - Pending debounced flushes (5s daemon delay)
+#
+# Installation:
+#   cp examples/git-hooks/pre-push .git/hooks/pre-push
+#   chmod +x .git/hooks/pre-push
+#
+# Or use the install script:
+#   examples/git-hooks/install.sh
+
+# Check if we're in a bd workspace
+if [ ! -d .beads ]; then
+    # Not a bd workspace, nothing to do
+    exit 0
+fi
+
+# Optionally flush pending bd changes so they surface in JSONL
+# This prevents the race where a debounced flush lands after the check
+if command -v bd >/dev/null 2>&1; then
+    bd sync --flush-only >/dev/null 2>&1 || true
+fi
+
+# Collect all tracked or existing JSONL files (supports both old and new names)
+FILES=""
+for f in .beads/beads.jsonl .beads/issues.jsonl; do
+    # Include file if it exists in working tree OR is tracked by git (even if deleted)
+    if git ls-files --error-unmatch "$f" >/dev/null 2>&1 || [ -f "$f" ]; then
+        FILES="$FILES $f"
+    fi
+done
+
+# Check for any uncommitted changes using porcelain status
+# This catches: staged, unstaged, untracked, deleted, renamed, and conflicts
+if [ -n "$FILES" ]; then
+    # shellcheck disable=SC2086
+    if [ -n "$(git status --porcelain -- $FILES 2>/dev/null)" ]; then
+        echo "❌ Error: Beads JSONL has uncommitted changes" >&2
+        echo "" >&2
+        echo "You made changes to bd issues between your last commit and this push." >&2
+        echo "Please commit the updated JSONL before pushing:" >&2
+        echo "" >&2
+        # shellcheck disable=SC2086
+        echo "  git add $FILES" >&2
+        echo '  git commit -m "Update bd JSONL"' >&2
+        echo "  git push" >&2
+        echo "" >&2
+        exit 1
+    fi
+fi
+
+exit 0