Local-first runtime cleanup and recovery hardening

bible-local/06-backup.md

@@ -34,6 +34,11 @@ backup:
 - `QFS_BACKUP_DIR` — backup root directory (default: `<db dir>/backups`)
 - `QFS_BACKUP_DISABLE` — disable backups (`1/true/yes`)
 
+**Safety rules:**
+- Backup root must resolve outside any git worktree.
+- If `qfs.db` is placed inside a repository checkout, default backups are rejected until `QFS_BACKUP_DIR` points outside the repo.
+- Backup archives intentionally do **not** include `local_encryption.key`; restored installations on another machine must re-enter DB credentials.
+
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 ## Behavior
@@ -76,6 +81,7 @@ type BackupConfig struct {
 - `.period.json` is the marker that prevents duplicate backups within the same period
 - Archive filenames contain only the date; uniqueness is ensured by per-period directories + the period marker
 - When changing naming or retention: update both the filename logic and the prune logic together
+- Git worktree detection is path-based (`.git` ancestor check) and blocks backup creation inside the repo tree
 
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