feat: add group chat activation mode

docs/configuration.md

@@ -73,13 +73,13 @@ Allowlist of E.164 phone numbers that may trigger auto-replies.
 
 ### `inbound.groupChat`
 
-Group messages default to **require mention** (either metadata mention or regex patterns).
+Group messages default to **require mention** (either metadata mention or regex patterns). You can switch to always-on activation.
 
 ```json5
 {
   inbound: {
     groupChat: {
-      requireMention: true,
+      activation: "mention", // mention | always
       mentionPatterns: ["@clawd", "clawdbot", "clawd"],
       historyLimit: 50
     }
@@ -87,6 +87,10 @@ Group messages default to **require mention** (either metadata mention or regex
 }
 ```
 
+Notes:
+- `activation` defaults to `mention`.
+- `requireMention` is still supported for backwards compatibility (`false` ≈ `activation: "always"`).
+
 ### `inbound.workspace`
 
 Sets the **single global workspace directory** used by the agent for file operations.