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.

internal/config/loader.go

@@ -0,0 +1,101 @@
+package config
+
+import (
+	"fmt"
+	"os"
+
+	"gopkg.in/yaml.v3"
+)
+
+// Load reads and parses an agent config file from the given path.
+func Load(path string) (*AgentConfig, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("read config %s: %w", path, err)
+	}
+
+	// Expand environment variables in the raw YAML bytes.
+	expanded := os.ExpandEnv(string(data))
+
+	var cfg AgentConfig
+	if err := yaml.Unmarshal([]byte(expanded), &cfg); err != nil {
+		return nil, fmt.Errorf("parse config %s: %w", path, err)
+	}
+
+	if err := validate(&cfg); err != nil {
+		return nil, fmt.Errorf("invalid config %s: %w", path, err)
+	}
+
+	return &cfg, nil
+}
+
+// LoadMeta reads only the `agent:` block from a config file without expanding
+// env vars or running full validation. Used by agentctl list to show all
+// agents regardless of whether their env vars are configured.
+func LoadMeta(path string) (*AgentConfig, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("read config %s: %w", path, err)
+	}
+	var cfg AgentConfig
+	if err := yaml.Unmarshal(data, &cfg); err != nil {
+		return nil, fmt.Errorf("parse config %s: %w", path, err)
+	}
+	if cfg.Agent.ID == "" {
+		return nil, fmt.Errorf("agent.id is required")
+	}
+	return &cfg, nil
+}
+
+// LoadSpecial reads and parses a special agent config file.
+// Special agents have no Matrix identity so validation is lighter.
+func LoadSpecial(path string) (*SpecialConfig, error) {
+	data, err := os.ReadFile(path)
+	if err != nil {
+		return nil, fmt.Errorf("read special config %s: %w", path, err)
+	}
+
+	expanded := os.ExpandEnv(string(data))
+
+	var cfg SpecialConfig
+	if err := yaml.Unmarshal([]byte(expanded), &cfg); err != nil {
+		return nil, fmt.Errorf("parse special config %s: %w", path, err)
+	}
+
+	if err := validateSpecial(&cfg); err != nil {
+		return nil, fmt.Errorf("invalid special config %s: %w", path, err)
+	}
+
+	return &cfg, nil
+}
+
+// validateSpecial applies sanity checks for special agent configs.
+func validateSpecial(cfg *SpecialConfig) error {
+	if cfg.Special.ID == "" {
+		return fmt.Errorf("special.id is required")
+	}
+	if cfg.Special.Type == "" {
+		return fmt.Errorf("special.type is required")
+	}
+	if cfg.LLM.Primary.Provider == "" {
+		return fmt.Errorf("llm.primary.provider is required")
+	}
+	return nil
+}
+
+// validate applies basic sanity checks.
+func validate(cfg *AgentConfig) error {
+	if cfg.Agent.ID == "" {
+		return fmt.Errorf("agent.id is required")
+	}
+	if cfg.Bus.NatsURL == "" {
+		return fmt.Errorf("bus.nats_url is required")
+	}
+	if cfg.Bus.CtrlURL == "" {
+		return fmt.Errorf("bus.ctrl_url is required")
+	}
+	if cfg.LLM.Primary.Provider == "" {
+		return fmt.Errorf("llm.primary.provider is required")
+	}
+	return nil
+}