Fix: remove agent from pool immediately on completion and add Matrix bot user allowlist

server/src/matrix/config.rs

@@ -15,6 +15,10 @@ pub struct BotConfig {
     /// Set to `true` to enable the bot (default: false)
     #[serde(default)]
     pub enabled: bool,
+    /// Matrix user IDs allowed to interact with the bot.
+    /// If empty or omitted, the bot ignores ALL messages (fail-closed).
+    #[serde(default)]
+    pub allowed_users: Vec<String>,
     /// Previously used to select an Anthropic model. Now ignored — the bot
     /// uses Claude Code which manages its own model selection. Kept for
     /// backwards compatibility so existing bot.toml files still parse.