upwatch: hold a seeding torrent app for one line test, then put its limit back exactly (R-1250)

When the agent waits for quiet and qBittorrent or Transmission runs: record the limit first,
hold at 1 KiB/s, ask the agent for a test on request, put the old limit back (deferred; a
household change during the test stays). Start-up puts back a limit a killed controller left;
the 50 % rule skips while a hold record exists. Commit only.

controller/internal/upwatch/service.go

@@ -14,6 +14,8 @@ import (
 type State struct {
 	Line    []LineRecord  `json:"line,omitempty"`
 	QBLimit *QBLimitState `json:"qb_limit,omitempty"`
+	// Hold is a torrent app held low for a line test on request (R-1250, linehold.go); nil when none.
+	Hold *LineHold `json:"line_test_hold,omitempty"`
 }
 
 // Store is the settings half the service needs (settings.Settings satisfies it).
@@ -44,7 +46,14 @@ type Service struct {
 	// to ep0 inside the tunnel. nil or ok=false = not measured. Read every 15 minutes (RefreshMeasured), never per
 	// minute.
 	Measured func(ctx context.Context) (mbps float64, at time.Time, ok bool)
-	Log      *log.Logger
+	// The line test for a box that seeds all day (R-1250, linehold.go). Torrents are the apps that can be held, in
+	// order of preference; TorrentRunning says whether one runs now; LineWaiting is the agent's waiting_for_quiet;
+	// LineRun is its test on request. Any nil = no hold.
+	Torrents       []Holdable
+	TorrentRunning func(stack string) bool
+	LineWaiting    func(ctx context.Context) bool
+	LineRun        func(ctx context.Context) (LineRunResult, error)
+	Log            *log.Logger
 
 	mu         sync.Mutex
 	measured   float64
@@ -137,6 +146,12 @@ func (s *Service) QBLimitNow(ctx context.Context) {
 	s.RefreshMeasured(ctx)
 	line, known := s.MeasuredLine()
 	cur := decode(s.Store.GetUpwatch())
+	if cur.Hold != nil {
+		// A line-test hold is in place or was left behind: qBittorrent holds the test value, which the rule would
+		// read as the household's change and then never touch the limit again (linehold.go).
+		logx.Debugf(s.Log, "[upwatch] qBittorrent limit: a line-test hold record exists — rule skipped until it is cleared")
+		return
+	}
 	var st QBLimitState
 	if cur.QBLimit != nil {
 		st = *cur.QBLimit