feat: initial mosaic bootstrap framework

templates/repo/scripts/agent/session-start.sh

@@ -0,0 +1,19 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+# shellcheck source=./common.sh
+source "$SCRIPT_DIR/common.sh"
+
+ensure_repo_root
+load_repo_hooks
+
+if git rev-parse --is-inside-work-tree >/dev/null 2>&1 && has_remote; then
+  run_step "Pull latest changes" git pull --rebase
+fi
+
+if declare -F mosaic_hook_session_start >/dev/null 2>&1; then
+  run_step "Run repo start hook" mosaic_hook_session_start
+else
+  echo "[agent-framework] No repo start hook configured (.mosaic/repo-hooks.sh)"
+fi