story-kit: merge 277 - bot uses configured display_name

Adds system_prompt parameter to chat_stream so the Matrix bot
passes "Your name is {name}" to Claude Code. Reads display_name
from bot.toml config. Resolved conflicts by integrating bot_name
into master's permission-handling code structure.

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

server/src/matrix/bot.rs

@@ -162,6 +162,9 @@ pub struct BotContext {
     /// How long to wait for a user to respond to a permission prompt before
     /// denying (fail-closed).
     pub permission_timeout_secs: u64,
+    /// The name the bot uses to refer to itself. Derived from `display_name`
+    /// in bot.toml; defaults to "Assistant" when unset.
+    pub bot_name: String,
 }
 
 // ---------------------------------------------------------------------------
@@ -313,6 +316,11 @@ pub async fn run_bot(
         persisted.len()
     );
 
+    let bot_name = config
+        .display_name
+        .clone()
+        .unwrap_or_else(|| "Assistant".to_string());
+
     let ctx = BotContext {
         bot_user_id,
         target_room_ids,
@@ -324,6 +332,7 @@ pub async fn run_bot(
         perm_rx,
         pending_perm_replies: Arc::new(TokioMutex::new(HashMap::new())),
         permission_timeout_secs: config.permission_timeout_secs,
+        bot_name,
     };
 
     slog!("[matrix-bot] Cryptographic identity verification is always ON — commands from unencrypted rooms or unverified devices are rejected");
@@ -741,6 +750,11 @@ async fn handle_message(
     // Prior conversation context is carried by the Claude Code session.
     let prompt = format_user_prompt(&sender, &user_message);
 
+    let bot_name = &ctx.bot_name;
+    let system_prompt = format!(
+        "Your name is {bot_name}. Refer to yourself as {bot_name}, not Claude."
+    );
+
     let provider = ClaudeCodeProvider::new();
     let (cancel_tx, mut cancel_rx) = watch::channel(false);
     // Keep the sender alive for the duration of the call.
@@ -778,6 +792,7 @@ async fn handle_message(
         &prompt,
         &project_root_str,
         resume_session_id.as_deref(),
+        Some(&system_prompt),
         &mut cancel_rx,
         move |token| {
             let mut buf = buffer_for_callback.lock().unwrap();
@@ -1205,6 +1220,7 @@ mod tests {
             perm_rx: Arc::new(TokioMutex::new(perm_rx)),
             pending_perm_replies: Arc::new(TokioMutex::new(HashMap::new())),
             permission_timeout_secs: 120,
+            bot_name: "Assistant".to_string(),
         };
         // Clone must work (required by Matrix SDK event handler injection).
         let _cloned = ctx.clone();
@@ -1638,8 +1654,6 @@ mod tests {
 
     #[test]
     fn is_permission_approval_strips_at_mention_prefix() {
-        // "@botname yes" should still be treated as approval — the mention
-        // prefix is stripped before checking the token.
         assert!(is_permission_approval("@timmy yes"));
         assert!(!is_permission_approval("@timmy no"));
     }
@@ -1649,4 +1663,28 @@ mod tests {
         assert!(is_permission_approval("  yes  "));
         assert!(is_permission_approval("\tyes\n"));
     }
+
+    // -- bot_name / system prompt -------------------------------------------
+
+    #[test]
+    fn bot_name_system_prompt_format() {
+        let bot_name = "Timmy";
+        let system_prompt =
+            format!("Your name is {bot_name}. Refer to yourself as {bot_name}, not Claude.");
+        assert_eq!(
+            system_prompt,
+            "Your name is Timmy. Refer to yourself as Timmy, not Claude."
+        );
+    }
+
+    #[test]
+    fn bot_name_defaults_to_assistant_when_display_name_absent() {
+        // When display_name is not set in bot.toml, bot_name should be "Assistant".
+        // This mirrors the logic in run_bot: config.display_name.clone().unwrap_or_else(...)
+        fn resolve_bot_name(display_name: Option<String>) -> String {
+            display_name.unwrap_or_else(|| "Assistant".to_string())
+        }
+        assert_eq!(resolve_bot_name(None), "Assistant");
+        assert_eq!(resolve_bot_name(Some("Timmy".to_string())), "Timmy");
+    }
 }