v0.318.0: the internal data place, partitions, an honest whole-box backup offer (R-1084), sys_drive never offered (R-1082)

felhom.eu architecture/16 §4-§6 (build B). MinAgent 0.157.0 — the internal place and the partitions appear only when
agent >= 0.158.0 reports them. Tests red-proved; four parity fixtures refreshed (only the new lines).

Claude-Session: https://claude.ai/code/session_012qRErfCoiTkvDK9N5XHbzb

controller/internal/web/server.go

@@ -251,6 +251,11 @@ type Server struct {
 	// pure copy helper. Without it the resolver's own branching had no test at all, which is how the
 	// configured-but-absent case reached production saying the wrong thing.
 	tiersFn func(context.Context) (agentapi.TiersResponse, error)
+	// sameDiskFn (R-1084, v0.318.0) is the test seam for the backup-target offer's same-disk question
+	// (nil → the real agent client, POST /disks/same-disk).
+	sameDiskFn func(ctx context.Context, drive, systemData string) offerRelation
+	// mountsFn (v0.318.0) is the test seam for the guest's mount table (nil → /proc/mounts).
+	mountsFn func() string
 
 	// App-email SMTP shim lifecycle (optional — nil when no hub is configured or the kill-switch is
 	// off). The global app-email settings toggle calls Apply() so the shim starts/stops at runtime.