Merge pull request 'chore: remove .DS_Store artifacts and fix .gitignore' (#4) from claude/silly-robinson into main

Reviewed-on: #4

.gitignore

@@ -108,4 +108,3 @@ yarn-error.log*
 
 # Allow keeping empty dirs with .keep
 !.keep
-freebsd/prototypes/.DS_Store

cmd/ledger-demo/main.go

@@ -0,0 +1,56 @@
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"os"
+	"time"
+
+	"shadowmo/Cognition-OS/runtime/ledger"
+)
+
+func main() {
+	path := flag.String("file", "ledger-demo.jsonl", "path to ledger file")
+	op := flag.String("op", "append", "operation: append|verify|show")
+	flag.Parse()
+
+	l, err := ledger.Open(*path)
+	if err != nil {
+		fmt.Fprintln(os.Stderr, "open error:", err)
+		os.Exit(1)
+	}
+	defer l.Close()
+
+	switch *op {
+	case "append":
+		payload := map[string]interface{}{
+			"msg": fmt.Sprintf("demo event at %s", time.Now().Format(time.RFC3339)),
+		}
+		h, err := l.Append("demo_event", payload)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, "append error:", err)
+			os.Exit(1)
+		}
+		fmt.Println("appended hash:", h)
+	case "verify":
+		if err := l.Verify(); err != nil {
+			fmt.Fprintln(os.Stderr, "verify failed:", err)
+			os.Exit(2)
+		}
+		fmt.Println("ledger verified ok")
+	case "show":
+		f, err := os.Open(*path)
+		if err != nil { fmt.Fprintln(os.Stderr, "open:", err); os.Exit(1) }
+		defer f.Close()
+		dec := json.NewDecoder(f)
+		for {
+			var e map[string]interface{}
+			if err := dec.Decode(&e); err != nil { break }
+			b, _ := json.MarshalIndent(e, "", "  ")
+			fmt.Println(string(b))
+		}
+	default:
+		fmt.Fprintln(os.Stderr, "unknown op")
+	}
+}