feat: import agents_and_robots platform as unibots (Matrix-out, unibus transport)

Reemplaza el scaffold del echobot por la plataforma completa de bots traida
desde ~/DataProyects/Github/agents_and_robots tras la operacion Matrix-out:
los bots ya no hablan por Matrix sino por el bus unibus (modelo todo-rooms +
E2E via shell/transportunibus sobre github.com/enmanuel/unibus/pkg/client).

- go.mod: replace de unibus -> ../unibus y de fn-registry -> ../../../.. (paths
  relativos reajustados a la nueva ubicacion dentro de fn_registry).
- app.md: bump a 0.2.0, descripcion + arquitectura + comandos + gotchas reales.
- modulo Go conservado como github.com/enmanuel/agents (sin reescribir imports).

agents_and_robots queda archivado como museo de la era Matrix.

pkg/memory/window.go

@@ -0,0 +1,43 @@
+package memory
+
+import "github.com/enmanuel/agents/pkg/llm"
+
+// Window is an immutable sliding window of conversation messages for a single room.
+type Window struct {
+	messages []llm.Message
+	maxSize  int
+}
+
+// NewWindow creates an empty window with the given capacity.
+func NewWindow(maxSize int) Window {
+	return Window{maxSize: maxSize}
+}
+
+// Append returns a new Window with the message added, dropping the oldest
+// messages if capacity is exceeded.
+func (w Window) Append(msg llm.Message) Window {
+	msgs := make([]llm.Message, len(w.messages), len(w.messages)+1)
+	copy(msgs, w.messages)
+	msgs = append(msgs, msg)
+	if len(msgs) > w.maxSize {
+		msgs = msgs[len(msgs)-w.maxSize:]
+	}
+	return Window{messages: msgs, maxSize: w.maxSize}
+}
+
+// ToLLMMessages returns a copy of the window contents as []llm.Message.
+func (w Window) ToLLMMessages() []llm.Message {
+	out := make([]llm.Message, len(w.messages))
+	copy(out, w.messages)
+	return out
+}
+
+// Len returns the number of messages in the window.
+func (w Window) Len() int {
+	return len(w.messages)
+}
+
+// Clear returns an empty window with the same capacity.
+func (w Window) Clear() Window {
+	return NewWindow(w.maxSize)
+}