Add --shared flag to bd hooks install for versioned hooks

Implements support for installing git hooks to a versioned directory
(.beads-hooks/) that can be committed to the repository and shared with
team members. This solves the team collaboration issue where hooks need
to be installed in pre-built containers.

Changes:
- Add --shared flag to 'bd hooks install' command
- Install hooks to .beads-hooks/ when --shared is used
- Automatically configure git config core.hooksPath
- Update help text to explain shared mode

Fixes #229

.beads-hooks/post-merge

@@ -0,0 +1,45 @@
+#!/bin/sh
+# bd-hooks-version: 0.24.2
+#
+# 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
+# Capture both stdout and stderr to show user what went wrong
+if ! output=$(bd sync --import-only 2>&1); then
+    echo "Warning: Failed to sync bd changes after merge" >&2
+    echo "$output" >&2
+    echo "" >&2
+    echo "Run 'bd sync --import-only' manually to resolve" >&2
+    # Don't fail the merge, just warn
+fi
+
+exit 0