fix: remove no-op SaveJobs calls, fix PendingRuns lifecycle and cap

Implements items 4-5 of the whole-project review's suggested order
(docs/PROJECT_REVIEW_PLAN.md):

- Drop the three SaveJobs calls in the run lifecycle (startRunLocked,
  executeRun, SetGlobalPause): none of them change a durable Job field,
  everything they touch lives on JobRuntime, which is never persisted.
  Retire TestStartRunLockedRollbackOnSaveFailure with the rollback it
  guarded, since a run can no longer fail to start this way.
- Clear PendingRuns (the "queue" overlap policy's backlog) when a job is
  disabled or the scheduler is globally paused, so resuming or
  re-enabling a job no longer replays a deferred run left over from
  before the pause/disable. Cap it at maxPendingRuns (10) so a job whose
  runs take longer than its own interval stops accumulating an unbounded
  backlog. Surface the queued count in the details pane via DisplayStats.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/app/format.go

@@ -82,14 +82,29 @@ func DisplayInvocation(job domain.Job) string {
 	return job.Command + "    " + strings.ReplaceAll(strings.TrimSpace(job.Arguments), "\n", " ")
 }
 
-// DisplayStats returns a one-line execution-time summary for a job runtime.
-// Returns "No runs recorded" when no runs have been counted yet.
+// DisplayStats returns a one-line execution-time summary for a job runtime,
+// with the queued-run depth appended whenever the "queue" overlap policy has
+// deferred runs waiting (see maxPendingRuns). Returns "No runs recorded" when
+// no runs have been counted yet, still showing the queue depth if one exists.
 func DisplayStats(rt *domain.JobRuntime) string {
 	if rt == nil || rt.RunCount == 0 {
+		if rt != nil && rt.PendingRuns > 0 {
+			return "No runs recorded" + pendingRunsSuffix(rt.PendingRuns)
+		}
 		return "No runs recorded"
 	}
 	return fmt.Sprintf("%d runs, %d failed, last %d ms, avg %d ms, max %d ms",
-		rt.RunCount, rt.FailCount, rt.LastDurationMS, rt.AvgDurationMS, rt.MaxDurationMS)
+		rt.RunCount, rt.FailCount, rt.LastDurationMS, rt.AvgDurationMS, rt.MaxDurationMS) +
+		pendingRunsSuffix(rt.PendingRuns)
+}
+
+// pendingRunsSuffix formats the queued-run depth for DisplayStats, empty when
+// nothing is queued.
+func pendingRunsSuffix(pending int) string {
+	if pending <= 0 {
+		return ""
+	}
+	return fmt.Sprintf(", %d queued", pending)
 }
 
 // DisplayOverlapPolicy formats a job's effective overlap policy for the details