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/target_test.go

@@ -1,6 +1,7 @@
 package miner
 
 import (
+	"strings"
 	"testing"
 )
 
@@ -20,9 +21,50 @@ func TestHashMeetsTargetReject(t *testing.T) {
 	}
 }
 
-func TestDifficultyToTargetHex(t *testing.T) {
-	out := difficultyToTargetHex(1000)
-	if len(out) != 64 {
-		t.Fatalf("expected 64 hex chars, got %d", len(out))
+func TestHashMeetsTargetExactMatch(t *testing.T) {
+	val := "00000000000000000000000000000000000000000000000000000000000000ab"
+	if !hashMeetsTarget(val, val) {
+		t.Fatal("hash equal to target should meet target")
+	}
+}
+
+func TestHashMeetsTargetInvalidHex(t *testing.T) {
+	if hashMeetsTarget("not-hex", strings.Repeat("f", 64)) {
+		t.Fatal("invalid hash hex should not meet target")
+	}
+	if hashMeetsTarget(strings.Repeat("f", 64), "zz") {
+		t.Fatal("invalid target hex should not meet")
+	}
+	if hashMeetsTarget("", strings.Repeat("f", 64)) {
+		t.Fatal("empty hash should not meet target")
+	}
+}
+
+func TestHashMeetsTargetShortTargetPadded(t *testing.T) {
+	// Short target hex is zero-padded to hash width
+	target := "ff"
+	hash := strings.Repeat("0", 63) + "1"
+	if !hashMeetsTarget(hash, target) {
+		t.Fatal("padded short target should accept low hash")
+	}
+}
+
+func TestPadHex(t *testing.T) {
+	if got := padHex("ab", 6); got != "0000ab" {
+		t.Fatalf("padHex = %q", got)
+	}
+	if got := padHex("abcdef", 4); got != "abcdef" {
+		t.Fatalf("no truncate when already long: %q", got)
+	}
+}
+
+func TestReverseBytes(t *testing.T) {
+	in := []byte{1, 2, 3, 4}
+	out := reverseBytes(in)
+	want := []byte{4, 3, 2, 1}
+	for i := range want {
+		if out[i] != want[i] {
+			t.Fatalf("reverseBytes = %v, want %v", out, want)
+		}
 	}
 }