feat: add granular ACL tiers (trusted/oper/admin)

4-tier permission model: user < trusted < oper < admin.
Commands specify a required tier via tier= parameter.
Backward compatible: admin=True maps to tier="admin".

- TIERS constant and Handler.tier field in plugin.py
- _get_tier() method in bot.py with pattern matching
- _is_admin() preserved as thin wrapper
- operators/trusted config lists in config.py
- whoami shows tier, admins shows all configured tiers
- 32 test cases in test_acl.py

plugins/core.py

@@ -139,34 +139,33 @@ async def cmd_plugins(bot, message):
     await bot.reply(message, f"Plugins: {', '.join(parts)}")
 
 
-@command("whoami", help="Show your hostmask and admin status")
+@command("whoami", help="Show your hostmask and permission tier")
 async def cmd_whoami(bot, message):
     """Display the sender's hostmask and permission level."""
     prefix = message.prefix or "unknown"
-    is_admin = bot._is_admin(message)
-    is_oper = message.prefix in bot._opers if message.prefix else False
-    tags = []
-    if is_admin:
-        tags.append("admin")
-    else:
-        tags.append("user")
-    if is_oper:
+    tier = bot._get_tier(message)
+    tags = [tier]
+    if message.prefix and message.prefix in bot._opers:
         tags.append("IRCOP")
     await bot.reply(message, f"{prefix} [{', '.join(tags)}]")
 
 
-@command("admins", help="Show configured admin patterns and detected opers", admin=True)
+@command("admins", help="Show configured permission tiers and detected opers", admin=True)
 async def cmd_admins(bot, message):
-    """Display admin hostmask patterns and known IRC operators."""
+    """Display configured permission tiers and known IRC operators."""
     parts = []
     if bot._admins:
-        parts.append(f"Patterns: {', '.join(bot._admins)}")
+        parts.append(f"Admin: {', '.join(bot._admins)}")
     else:
-        parts.append("Patterns: (none)")
+        parts.append("Admin: (none)")
+    if bot._operators:
+        parts.append(f"Oper: {', '.join(bot._operators)}")
+    if bot._trusted:
+        parts.append(f"Trusted: {', '.join(bot._trusted)}")
     if bot._opers:
-        parts.append(f"Opers: {', '.join(sorted(bot._opers))}")
+        parts.append(f"IRCOPs: {', '.join(sorted(bot._opers))}")
     else:
-        parts.append("Opers: (none)")
+        parts.append("IRCOPs: (none)")
     await bot.reply(message, " | ".join(parts))