R-263 writer invariant pinned by an AST test; R-368 IsDefault comment exact (no binary change; burn-down)

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0159rPz1ZhFKsS53msqPYxtS

controller/internal/settings/settings.go

@@ -569,7 +569,7 @@ const NetworkMountRoot = "/mnt/felhom-drives"
 type StoragePath struct {
 	Path             string   `json:"path"`                        // e.g., "/mnt/hdd_1" (drive) or "/mnt/felhom-drives/<name>" (network)
 	Label            string   `json:"label,omitempty"`             // e.g., "Külső HDD 1TB"
-	IsDefault        bool     `json:"is_default,omitempty"`        // new apps use this by default
+	IsDefault        bool     `json:"is_default,omitempty"`        // the deploy FORM pre-selects it (templates/deploy.html); the deploy API applies no default (R-368)
 	Schedulable      bool     `json:"schedulable"`                 // whether new apps can be deployed here
 	AddedAt          string   `json:"added_at"`                    // RFC3339
 	Disconnected     bool     `json:"disconnected,omitempty"`      // true when drive detected as disconnected
@@ -1652,8 +1652,9 @@ func (s *Settings) SetSchedulable(path string, schedulable bool) error {
 }
 
 // SetBackupTarget assigns the whole-guest backup-target role to exactly one storage path, clearing it
-// from every other. This is the ONLY writer of StoragePath.BackupTarget — registration must never set
-// it (E-2 §3: a drive never acquires a role by appearing).
+// from every other. This is the ONLY writer that GRANTS StoragePath.BackupTarget (ClearBackupTarget also writes
+// the field, only ever false) — registration must never set it (E-2 §3: a drive never acquires a role by
+// appearing). Pinned by TestR263_OnlySetBackupTargetGrantsTheRole (a scan of every non-test file).
 //
 // Refusals, both structural rather than advisory:
 //   - a NETWORK share can never be the target. vzdump writes a multi-GB archive through the host, and