supervisor-go: add ledger package with Append/Read APIs, tests; refactor CLI to use package; update README

kernel/supervisor-go/ledger/ledger_test.go

@@ -0,0 +1,56 @@
+package ledger
+
+import (
+	"os"
+	"testing"
+)
+
+func TestAppendAndRead(t *testing.T) {
+	f, err := os.CreateTemp("", "ledger-test-*.jsonl")
+	if err != nil {
+		t.Fatalf("tempfile: %v", err)
+	}
+	path := f.Name()
+	f.Close()
+	defer os.Remove(path)
+
+	l := New(path, "stream-1")
+	// ensure empty read
+	evs, err := l.ReadAll()
+	if err != nil {
+		t.Fatalf("read empty: %v", err)
+	}
+	if len(evs) != 0 {
+		t.Fatalf("expected 0 events, got %d", len(evs))
+	}
+
+	e1, err := l.Append("route_decision", map[string]any{"tier": "fast"})
+	if err != nil {
+		t.Fatalf("append1: %v", err)
+	}
+	if l.LastHash == nil || *l.LastHash != e1.Hash {
+		t.Fatalf("lasthash not set after append1")
+	}
+
+	e2, err := l.Append("final_output_emitted", map[string]any{"result": "ok"})
+	if err != nil {
+		t.Fatalf("append2: %v", err)
+	}
+	if l.LastHash == nil || *l.LastHash != e2.Hash {
+		t.Fatalf("lasthash not set after append2")
+	}
+	if e2.PrevHash == nil || *e2.PrevHash != e1.Hash {
+		t.Fatalf("prevhash chain broken")
+	}
+
+	evs, err = l.ReadAll()
+	if err != nil {
+		t.Fatalf("read: %v", err)
+	}
+	if len(evs) != 2 {
+		t.Fatalf("expected 2 events, got %d", len(evs))
+	}
+	if evs[0].Hash != e1.Hash || evs[1].Hash != e2.Hash {
+		t.Fatalf("readback hashes mismatch")
+	}
+}