fix(jobs): timer leak in Module.Stop and warn on unknown runner names

Module.Stop used time.After which leaks the timer if the done channel
wins first; switch to time.NewTimer + defer Stop() to align with the
codebase convention.

scheduleEntry silently returned {0, false} for unknown runner names —
typos in production wiring were invisible. Return (entry, known) and
log Warn at NewModule registration time so misconfiguration surfaces.

internal/jobs/module.go

@@ -47,7 +47,10 @@ func NewModule(cfg Config, deps ModuleDeps) *Module {
 
 	sch := NewScheduler(log)
 	for name, fn := range deps.RunnerFns {
-		entry := scheduleEntry(cfg, name)
+		entry, known := scheduleEntry(cfg, name)
+		if !known {
+			log.Warn("jobs.module.unknown_runner", "name", name)
+		}
 		sch.Add(name, entry.interval, entry.enabled, fn)
 	}
 
@@ -95,10 +98,12 @@ func (m *Module) Stop(ctx context.Context) {
 	if grace <= 0 {
 		grace = 30 * time.Second
 	}
+	timer := time.NewTimer(grace)
+	defer timer.Stop()
 	select {
 	case <-done:
 		m.log.Info("jobs.module.stopped")
-	case <-time.After(grace):
+	case <-timer.C:
 		m.log.Warn("jobs.module.shutdown_timeout", "grace_ms", grace.Milliseconds())
 	case <-ctx.Done():
 		m.log.Warn("jobs.module.shutdown_ctx_canceled")
@@ -112,18 +117,18 @@ type schedEntry struct {
 	enabled  bool
 }
 
-func scheduleEntry(cfg Config, name string) schedEntry {
+func scheduleEntry(cfg Config, name string) (schedEntry, bool) {
 	switch name {
 	case "workspace_fetch":
-		return schedEntry{cfg.WorkspaceFetch.Interval, cfg.WorkspaceFetch.Enabled}
+		return schedEntry{cfg.WorkspaceFetch.Interval, cfg.WorkspaceFetch.Enabled}, true
 	case "worktree_prune":
-		return schedEntry{cfg.WorktreePrune.Interval, cfg.WorktreePrune.Enabled}
+		return schedEntry{cfg.WorktreePrune.Interval, cfg.WorktreePrune.Enabled}, true
 	case "attachment_cleanup":
-		return schedEntry{cfg.AttachmentCleanup.Interval, cfg.AttachmentCleanup.Enabled}
+		return schedEntry{cfg.AttachmentCleanup.Interval, cfg.AttachmentCleanup.Enabled}, true
 	case "job_reaper":
-		return schedEntry{cfg.JobReaper.Interval, cfg.JobReaper.Enabled}
+		return schedEntry{cfg.JobReaper.Interval, cfg.JobReaper.Enabled}, true
 	case "job_purge":
-		return schedEntry{cfg.JobPurge.Interval, cfg.JobPurge.Enabled}
+		return schedEntry{cfg.JobPurge.Interval, cfg.JobPurge.Enabled}, true
 	}
-	return schedEntry{0, false}
+	return schedEntry{0, false}, false
 }