fix: accept zero retention limits, retire Store() for typed accessors

Phase 8 (PROJECT_REVIEW_PLAN.md 8.1): 0 in MaxLogFiles/MaxLogAgeDays now
means "keep everything" end to end. runner.CleanupLogs already treated
<= 0 as disabled; validateConfig, the Settings form, and
loadOrCreateConfig's backfill were the only things making that state
unreachable.

Phase 9 (1.1, rolling up 1.2, 1.3, 7.3): added Service.Config() and
Service.Paths(), copying under mu, and converted every UI site that read
Service state through the raw *storage.Store returned by Store() (now
removed). jobs_view's pause control is now driven by refreshView reading
svc.Config().Paused on every event instead of only mirroring its own tap
handler, which makes it an actual consumer of SchedulerStateChanged.
mainwindow's event listener is a real type switch, and events.go's doc
comment no longer claims a compiler exhaustiveness check Go doesn't have.
Unexported the redundant SetAutostart/AutostartStatus package functions
in platform/autostart now that only the Manager methods are used outside
the package.

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

src/app/operations_test.go

@@ -522,9 +522,9 @@ func TestUpdateSettingsPersistsAndValidates(t *testing.T) {
 	svc := newTempService(t, nil)
 
 	bad := svc.store.Config
-	bad.MaxLogFiles = 0
+	bad.MaxLogFiles = -1
 	if err := svc.UpdateSettings(bad); err == nil {
-		t.Error("expected validation error for non-positive max log files")
+		t.Error("expected validation error for negative max log files")
 	}
 
 	good := svc.store.Config
@@ -533,8 +533,21 @@ func TestUpdateSettingsPersistsAndValidates(t *testing.T) {
 	if err := svc.UpdateSettings(good); err != nil {
 		t.Fatalf("UpdateSettings: %v", err)
 	}
-	if svc.Store().Config.MaxLogAgeDays != 7 || svc.Store().Config.NotifyOnFailure {
-		t.Errorf("config not applied: %+v", svc.Store().Config)
+	if svc.store.Config.MaxLogAgeDays != 7 || svc.store.Config.NotifyOnFailure {
+		t.Errorf("config not applied: %+v", svc.store.Config)
+	}
+
+	// 0 means "keep everything" (see STANDARDS §Intentional behavior), not an
+	// invalid value, so it must be accepted and persisted rather than rejected
+	// or silently backfilled.
+	unlimited := svc.store.Config
+	unlimited.MaxLogFiles = 0
+	unlimited.MaxLogAgeDays = 0
+	if err := svc.UpdateSettings(unlimited); err != nil {
+		t.Fatalf("UpdateSettings with zero retention limits: %v", err)
+	}
+	if svc.store.Config.MaxLogFiles != 0 || svc.store.Config.MaxLogAgeDays != 0 {
+		t.Errorf("zero retention limits not preserved: %+v", svc.store.Config)
 	}
 }
 
@@ -549,8 +562,8 @@ func TestUpdateSettingsRejectsInvalidConfigs(t *testing.T) {
 		{"missing jobs file", func(c *domain.Config) { c.JobsFile = "  " }},
 		{"jobs file without a file name", func(c *domain.Config) { c.JobsFile = "jobs" + string(filepath.Separator) }},
 		{"missing logs dir", func(c *domain.Config) { c.LogsDir = "" }},
-		{"non-positive max files", func(c *domain.Config) { c.MaxLogFiles = 0 }},
-		{"non-positive max age", func(c *domain.Config) { c.MaxLogAgeDays = -1 }},
+		{"negative max files", func(c *domain.Config) { c.MaxLogFiles = -1 }},
+		{"negative max age", func(c *domain.Config) { c.MaxLogAgeDays = -1 }},
 		{"negative default timeout", func(c *domain.Config) { c.DefaultTimeoutSeconds = -1 }},
 	}
 	for _, tc := range tests {
@@ -712,12 +725,12 @@ func TestUpdateSettingsRefusesJobsFileSwitchWhileRunning(t *testing.T) {
 	if err := svc.UpdateSettings(config); err == nil {
 		t.Error("expected the jobs-file switch to be refused while a job is running")
 	}
-	if svc.Store().Config.JobsFile == config.JobsFile {
+	if svc.store.Config.JobsFile == config.JobsFile {
 		t.Error("the refused switch must not have been persisted")
 	}
 
 	// A setting that does not touch the jobs file still saves during a run.
-	unrelated := svc.Store().Config
+	unrelated := svc.store.Config
 	unrelated.NotifyOnFailure = !unrelated.NotifyOnFailure
 	if err := svc.UpdateSettings(unrelated); err != nil {
 		t.Errorf("unrelated setting should still save during a run: %v", err)