feat(cli): add bridge conventions and link from actor errors

Surfaces the actor naming rules (adm-/agt-/atm- prefixes, legacy class
aliases) so users hitting a ConfigError have an in-CLI way to read the
spec without grepping the wiki.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/bridge/config.py

@@ -137,7 +137,8 @@ def _parse_actor_type(name: str, raw_class: str) -> ActorType:
     except ValueError:
         raise ConfigError(
             f"Actor '{name}' has unknown class '{raw_class}'; "
-            f"must be one of: adm, agt, atm (or legacy: human, automation)"
+            f"must be one of: adm, agt, atm (or legacy: human, automation). "
+            f"Run `bridge conventions` for the full naming rules."
         )
 
 
@@ -153,7 +154,8 @@ def _parse_actors(raw: dict) -> Dict[str, ActorInfo]:
         if not name.startswith(required_prefix):
             raise ConfigError(
                 f"Actor '{name}' has type '{actor_type.value}' but name must start "
-                f"with '{required_prefix}' (got '{name}')"
+                f"with '{required_prefix}' (got '{name}'). "
+                f"Run `bridge conventions` for the full naming rules."
             )
         actors[name] = ActorInfo(
             name=name,