feat: initial whatsmeow bot with command handler and context helpers

Core framework (Handler, Command, Default muxer) in core/ package.
Command self-registration via init() with blank imports in cmds/.
Context helpers (send, reply, download, upload) in context/ package.
Permission system with GROUP_ONLY / PRIVATE_ONLY checks.
WhatsApp client configured as Safari with history sync disabled.

cmds/misc/ping.go

@@ -0,0 +1,24 @@
+package misc
+
+import (
+	"fmt"
+	"time"
+
+	hc "neo/context"
+	"neo/core"
+)
+
+func init() { core.Default.Register(Ping) }
+
+var Ping = &core.Command{
+	Name:        "ping",
+	Aliases:     []string{"test", "tes", "p"},
+	Category:    "general",
+	Description: "Check bot response time",
+	Permissions: []core.Permission{core.PermissionGroupOnly},
+	Run: func(ctx *hc.Ctx) {
+		t := ctx.Event().Info.Timestamp
+		speed := time.Since(t).Milliseconds()
+		ctx.Reply(fmt.Sprintf("Pong! 🏓\n\nSpeed: %d ms", speed))
+	},
+}