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.

tools/tool.go

@@ -0,0 +1,65 @@
+// Package tools defines tool specifications (pure) and their execution functions (impure).
+// Each tool is a pair: Def (pure data) + ToolFunc (impure execution).
+// To add a new tool, create a file in this package and register it in the agent builder.
+package tools
+
+import "context"
+
+// Def is the pure specification of a tool — only data, no side effects.
+type Def struct {
+	Name        string
+	Description string
+	Parameters  []Param
+}
+
+// Param describes a single parameter accepted by a tool.
+type Param struct {
+	Name        string
+	Type        string // "string", "number", "boolean", "integer", "object", "array"
+	Description string
+	Required    bool
+}
+
+// Result holds the outcome of executing a tool.
+type Result struct {
+	Output string
+	Err    error
+}
+
+// ToolFunc is the impure function that actually executes the tool.
+type ToolFunc func(ctx context.Context, args map[string]any) Result
+
+// Tool bundles a pure definition with its impure implementation.
+type Tool struct {
+	Def  Def
+	Exec ToolFunc
+}
+
+// GetString extracts a string argument by name, returning "" if missing or wrong type.
+func GetString(args map[string]any, key string) string {
+	v, ok := args[key]
+	if !ok {
+		return ""
+	}
+	s, ok := v.(string)
+	if !ok {
+		return ""
+	}
+	return s
+}
+
+// GetInt extracts an integer argument by name, returning 0 if missing or wrong type.
+func GetInt(args map[string]any, key string) int {
+	v, ok := args[key]
+	if !ok {
+		return 0
+	}
+	switch n := v.(type) {
+	case float64:
+		return int(n)
+	case int:
+		return n
+	default:
+		return 0
+	}
+}