feat: implementar tipo Robot como runtime ligero para bots command-only

Introduce la separacion Robot vs Agent en el sistema:

- agents/types.go: interfaz Runner comun (Run, Stop, Done, RegisterCommand)
  que tanto Agent como Robot satisfacen
- agents/robot.go: struct Robot — runtime minimo que solo conecta a Matrix
  y despacha comandos. Sin LLM, reglas, memoria, knowledge, skills ni tools.
  Mensajes normales se ignoran silenciosamente
- internal/config/schema.go: campo Type en AgentMeta ("agent"|"robot")
- cmd/launcher: usa Runner interface para manejar ambos tipos uniformemente.
  Si cfg.Agent.Type == "robot" crea NewRobot en vez de New (tanto en
  arranque como en hot-reload)
- agents/_template_robot/config.yaml: plantilla minima (~55 lineas) para
  robots command-only

El Robot soporta built-in commands reducidos (help, ping, status, info,
version) y comandos custom via RegisterCommand. No incluye tools, tool,
clear ni prompts ya que no tiene LLM ni memoria.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

agents/_template_robot/config.yaml

@@ -0,0 +1,57 @@
+# ============================================
+# ROBOT PLANTILLA (command-only, sin LLM)
+# ============================================
+# Referencia canonica para robots. NO se lanza (template: true).
+# Un robot solo responde a comandos (!xxx). Mensajes normales se ignoran.
+# Copiar y adaptar para nuevos robots.
+
+agent:
+  id: "_template_robot"
+  name: "Template Robot"
+  version: "0.0.0"
+  type: robot                  # robot = command-only, sin LLM ni reglas
+  enabled: true
+  template: true               # el launcher ignora este robot
+  description: "Robot plantilla. No se lanza."
+  tags: [template, robot]
+
+# ============================================
+# PERSONALIDAD (minima para robots)
+# ============================================
+personality:
+  prefix: ""
+  language: es
+
+# ============================================
+# MATRIX
+# ============================================
+matrix:
+  homeserver: "https://matrix.example.com"
+  user_id: "@robot:matrix.example.com"
+  access_token_env: MATRIX_TOKEN_ROBOT
+  device_id: "DEVICEID"
+
+  encryption:
+    enabled: false
+    store_path: "./agents/_template_robot/data/crypto/"
+    pickle_key_env: PICKLE_KEY_ROBOT
+    trust_mode: tofu
+    recovery_key_env: ""
+
+  rooms:
+    listen: []
+    respond: []
+    admin: []
+
+  filters:
+    command_prefix: "!"
+    mention_respond: false      # robots no responden a menciones (no hay LLM)
+    dm_respond: false           # robots no responden a DMs (no hay LLM)
+    ignore_bots: true
+    ignore_users: []
+    unauthorized_response: silent
+    min_power_level: 0
+
+  threads:
+    enabled: true
+    auto_thread: false