Expand test coverage across server, agent, and web; fix bugs found during audit.

Adds hundreds of unit/integration/e2e tests, fixes WS bcrypt auth, config merge, fleet analytics, agent schedule/log tail, and documents stale PROBLEMS items. Updates PROBLEMS.md, README, and test scripts; ignores local spread-kits and coverage dirs.

agent/stats/reporter_linux_test.go

@@ -0,0 +1,14 @@
+//go:build linux
+
+package stats
+
+import "testing"
+
+func TestParseKB(t *testing.T) {
+	if got := parseKB("MemTotal:       16384000 kB"); got != 16384000 {
+		t.Fatalf("got %d", got)
+	}
+	if parseKB("short") != 0 {
+		t.Fatal("invalid line should return 0")
+	}
+}

agent/stats/reporter_test.go

@@ -0,0 +1,49 @@
+package stats
+
+import (
+	"runtime"
+	"testing"
+)
+
+func TestNewReporterSystemInfo(t *testing.T) {
+	r := NewReporter()
+	host, cores, memGB := r.SystemInfo()
+	if host == "" {
+		t.Fatal("hostname should not be empty")
+	}
+	if cores < 1 {
+		t.Fatalf("cores %d", cores)
+	}
+	if memGB < 1 {
+		t.Fatalf("memoryGB %d", memGB)
+	}
+}
+
+func TestReporterUsage(t *testing.T) {
+	r := NewReporter()
+	cpu, mem := r.Usage()
+	if cpu < 0 || mem < 0 || mem > 100 {
+		t.Fatalf("cpu=%v mem=%v", cpu, mem)
+	}
+}
+
+func TestReporterMemoryMB(t *testing.T) {
+	r := NewReporter()
+	total := r.TotalMemoryMB()
+	free := r.FreeMemoryMB()
+	if runtime.GOOS == "windows" || runtime.GOOS == "linux" || runtime.GOOS == "darwin" {
+		if total == 0 {
+			t.Fatal("expected non-zero total memory on supported platform")
+		}
+	}
+	if free > total && total > 0 {
+		t.Fatalf("free %d > total %d", free, total)
+	}
+}
+
+func TestReporterSystemCPUPercentNonNegative(t *testing.T) {
+	r := NewReporter()
+	if pct := r.SystemCPUPercent(); pct < 0 {
+		t.Fatalf("negative cpu percent: %v", pct)
+	}
+}