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/command/prompts.go

@@ -0,0 +1,51 @@
+package command
+
+import (
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// PromptCommand maps a command name to its prompt content loaded from a .md file.
+type PromptCommand struct {
+	Name    string // filename without .md extension
+	Content string // file content (the prompt text)
+}
+
+// LoadPromptCommands scans dir for .md files and returns one PromptCommand per file.
+// Returns nil (no error) if the directory does not exist.
+func LoadPromptCommands(dir string) ([]PromptCommand, error) {
+	entries, err := os.ReadDir(dir)
+	if err != nil {
+		if os.IsNotExist(err) {
+			return nil, nil
+		}
+		return nil, err
+	}
+
+	var prompts []PromptCommand
+	for _, e := range entries {
+		if e.IsDir() || !strings.HasSuffix(e.Name(), ".md") {
+			continue
+		}
+		data, err := os.ReadFile(filepath.Join(dir, e.Name()))
+		if err != nil {
+			continue
+		}
+		name := strings.TrimSuffix(e.Name(), ".md")
+		prompts = append(prompts, PromptCommand{
+			Name:    name,
+			Content: strings.TrimSpace(string(data)),
+		})
+	}
+	return prompts, nil
+}
+
+// ExpandPrompt builds the final message by concatenating the prompt content
+// with any extra arguments the user provided after the command.
+func ExpandPrompt(content string, args []string) string {
+	if len(args) == 0 {
+		return content
+	}
+	return content + "\n\n" + strings.Join(args, " ")
+}