feat(db): add database backup/restore tooling

- tooling/db-backup: copies shared settledreach.db to docs/backups/
  for git tracking (main branch only)
- tooling/db-install: restores from backup for new clones
- make db-backup / make db-install Makefile targets
- worktree-update skill runs make db-backup after merges on main

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.claude/skills/worktree-update/SKILL.md

@@ -88,6 +88,18 @@ continue to the next branch. The user must resolve before proceeding.
 After all merges, show the final state with `git log --oneline -N` (where N
 covers the new commits).
 
+#### Backup the shared database
+
+After successful merges on main, snapshot the database for git tracking:
+
+```bash
+make db-backup
+```
+
+This copies the shared `settledreach.db` (in the parent directory) to
+`docs/backups/settledreach.db.backup`. Stage and commit it with the merge
+if the file changed.
+
 ### 2b. Not on `main` — merge main into current branch
 
 ```bash

Makefile

@@ -1,7 +1,8 @@
 GODOT := $(shell command -v godot4 2>/dev/null || command -v godot 2>/dev/null)
 
 .PHONY: help setup build client server test lint ci ci-client ci-server clean \
-       decisions-sync decisions-coverage decisions-active decisions-orphan
+       decisions-sync decisions-coverage decisions-active decisions-orphan \
+       db-backup db-install
 
 # --- Configuration ---
 
@@ -22,6 +23,9 @@ help:
 	@echo "  make ci-server      Run server CI checks"
 	@echo "  make clean          Remove build artifacts and caches"
 	@echo ""
+	@echo "  make db-backup          Backup shared database to git (main only)"
+	@echo "  make db-install         Restore shared database from backup"
+	@echo ""
 	@echo "  make decisions-sync     Sync decisions/*.md into SQLite"
 	@echo "  make decisions-coverage Decision-to-ticket coverage by domain"
 	@echo "  make decisions-active   List active decisions"
@@ -101,6 +105,14 @@ ci-server: lint-server build-server test-server
 
 ci-client: lint-client build-client test-client
 
+# --- Database ---
+
+db-backup:
+	@tooling/db-backup
+
+db-install:
+	@tooling/db-install
+
 # --- Decisions ---
 
 decisions-sync:

tooling/db-backup

@@ -0,0 +1,23 @@
+#!/usr/bin/env bash
+# Copy the shared database into git-tracked docs/backups/ for disaster recovery.
+# Only runs on the main branch — called via `make db-backup`.
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+WORKTREE_ROOT="$(dirname "$SCRIPT_DIR")"
+DB_PATH="$(dirname "$WORKTREE_ROOT")/settledreach.db"
+BACKUP_PATH="$WORKTREE_ROOT/docs/backups/settledreach.db.backup"
+
+branch="$(git -C "$WORKTREE_ROOT" branch --show-current)"
+if [ "$branch" != "main" ]; then
+    echo "error: db-backup only runs on the main branch (currently on '$branch')" >&2
+    exit 1
+fi
+
+if [ ! -f "$DB_PATH" ]; then
+    echo "error: shared database not found at $DB_PATH" >&2
+    exit 1
+fi
+
+cp "$DB_PATH" "$BACKUP_PATH"
+echo "ok: backed up $(du -h "$BACKUP_PATH" | cut -f1) to docs/backups/settledreach.db.backup"

tooling/db-install

@@ -0,0 +1,25 @@
+#!/usr/bin/env bash
+# Restore the shared database from the git-tracked backup.
+# Use after cloning or when the shared database is missing.
+# Called via `make db-install`.
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "$0")" && pwd)"
+WORKTREE_ROOT="$(dirname "$SCRIPT_DIR")"
+DB_PATH="$(dirname "$WORKTREE_ROOT")/settledreach.db"
+BACKUP_PATH="$WORKTREE_ROOT/docs/backups/settledreach.db.backup"
+
+if [ -f "$DB_PATH" ]; then
+    echo "error: shared database already exists at $DB_PATH" >&2
+    echo "       delete it first if you want to restore from backup" >&2
+    exit 1
+fi
+
+if [ ! -f "$BACKUP_PATH" ]; then
+    echo "error: backup not found at $BACKUP_PATH" >&2
+    echo "       run 'make db-backup' on the main branch first" >&2
+    exit 1
+fi
+
+cp "$BACKUP_PATH" "$DB_PATH"
+echo "ok: restored $(du -h "$DB_PATH" | cut -f1) to $DB_PATH"