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/miner/engine_test.go

@@ -0,0 +1,54 @@
+package miner
+
+import (
+	"strings"
+	"testing"
+)
+
+func TestNewEngineNotNil(t *testing.T) {
+	e := NewEngine()
+	if e == nil || e.cache == nil {
+		t.Fatal("NewEngine should allocate cache")
+	}
+}
+
+func TestEngineSetJobInvalidSeed(t *testing.T) {
+	e := NewEngine()
+	if err := e.SetJob("zz", strings.Repeat("00", 76)); err == nil {
+		t.Fatal("invalid seed hex should error")
+	}
+}
+
+func TestEngineSetJobInvalidBlob(t *testing.T) {
+	e := NewEngine()
+	seed := strings.Repeat("ab", 32)
+	if err := e.SetJob(seed, "not-hex"); err == nil {
+		t.Fatal("invalid blob hex should error")
+	}
+}
+
+func TestEngineHashAtNonceNoVM(t *testing.T) {
+	e := NewEngine()
+	hash, blob, err := e.HashAtNonce(0)
+	if err != nil {
+		t.Fatalf("unexpected error: %v", err)
+	}
+	if hash != "" || blob != "" {
+		t.Fatalf("empty VM should return empty strings, got hash=%q blob=%q", hash, blob)
+	}
+}
+
+func TestEngineHashAtNonceShortBlob(t *testing.T) {
+	e := NewEngine()
+	seed := strings.Repeat("cd", 32)
+	if err := e.SetJob(seed, strings.Repeat("00", 20)); err != nil {
+		t.Fatal(err)
+	}
+	hash, blob, err := e.HashAtNonce(1)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if hash != "" || blob != "" {
+		t.Fatalf("blob shorter than nonce offset should not hash, got hash=%q blob=%q", hash, blob)
+	}
+}