fix(tools): complete the bash shell alias in the tool codec

The tool dispatcher already treats `bash`/`Bash` as an alias of `Shell`
(routing, `is_shell_tool`, and `block_until_ms` normalization), but the
codec only matched `shell`:

- `tool_placeholder` returned `unsupported tool: bash`, which aborts the
  turn while streaming the tool call, before it ever runs;
- `request` returned `tool bash is not executed through ExecServerMessage`
  (after already reserving an exec slot); and
- `stream_closed` built its shell-specific error result only for `Shell`.

Anthropic models frequently emit `Bash` even when the tool is advertised
as `Shell`, so the alias must hold across the codec. Match `bash` wherever
the codec special-cases `shell`.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/src/cursor/tools/codec/render.rs

@@ -167,7 +167,7 @@ pub fn tool_completed(call: &ToolCall, completion: &ToolCompletion) -> pb::Agent
 pub fn tool_placeholder(name: &str, call_id: &str) -> Result<pb::ToolCall> {
     use pb::tool_call::Tool;
     let tool = match normalized(name).as_str() {
-        "shell" => Tool::ShellToolCall(pb::ShellToolCall::default()),
+        "shell" | "bash" => Tool::ShellToolCall(pb::ShellToolCall::default()),
         "delete" => Tool::DeleteToolCall(pb::DeleteToolCall::default()),
         "glob" => Tool::GlobToolCall(pb::GlobToolCall::default()),
         "grep" => Tool::GrepToolCall(pb::GrepToolCall::default()),
@@ -527,3 +527,23 @@ fn now_ms() -> u64 {
         .unwrap_or_default()
         .as_millis() as u64
 }
+
+#[cfg(test)]
+mod tests {
+    use super::tool_placeholder;
+    use crate::cursor::protocol::proto::agent::v1 as pb;
+
+    #[test]
+    fn bash_renders_as_a_shell_placeholder() {
+        // The dispatcher treats `bash`/`Bash` as a Shell alias, so the streaming
+        // placeholder must too; otherwise a `Bash` tool call aborts the turn with
+        // `unsupported tool: bash` before it ever runs.
+        for name in ["shell", "Shell", "bash", "Bash"] {
+            let tool = tool_placeholder(name, "call-1").unwrap().tool;
+            assert!(
+                matches!(tool, Some(pb::tool_call::Tool::ShellToolCall(_))),
+                "{name} should render as a Shell tool"
+            );
+        }
+    }
+}

server/src/cursor/tools/codec/request.rs

@@ -35,7 +35,7 @@ pub fn request(id: u32, call: &ToolCall, context: &ExecContext) -> Result<pb::Ag
             .map(|v| v as i32)
     };
     let message = match normalize(&call.name).as_str() {
-        "shell" => {
+        "shell" | "bash" => {
             let command = string("command")?;
             let (simple_commands, parsing_result) = shell_command_metadata(&command);
             Message::ShellStreamArgs(pb::ShellArgs {
@@ -520,3 +520,37 @@ fn prost_value(value: &Value) -> prost_types::Value {
     };
     ProstValue { kind: Some(kind) }
 }
+
+#[cfg(test)]
+mod tests {
+    use serde_json::json;
+
+    use super::request;
+    use crate::cursor::protocol::proto::agent::v1 as pb;
+    use crate::cursor::tools::runtime::ExecContext;
+    use crate::model::ToolCall;
+
+    #[test]
+    fn bash_is_encoded_as_a_shell_exec_request() {
+        // The dispatcher routes `bash`/`Bash` to the shell executor, so the
+        // request codec must encode it as a Shell stream instead of erroring
+        // with `tool bash is not executed through ExecServerMessage`.
+        let call = ToolCall {
+            index: 0,
+            call_id: "call-1".into(),
+            model_call_id: "model-1".into(),
+            name: "Bash".into(),
+            arguments_text: String::new(),
+            arguments: json!({ "command": "ls -la" }),
+        };
+        let message = request(1, &call, &ExecContext::default()).unwrap();
+        let Some(pb::agent_server_message::Message::ExecServerMessage(exec)) = message.message
+        else {
+            panic!("expected an ExecServerMessage");
+        };
+        let Some(pb::exec_server_message::Message::ShellStreamArgs(args)) = exec.message else {
+            panic!("expected ShellStreamArgs");
+        };
+        assert_eq!(args.command, "ls -la");
+    }
+}

server/src/cursor/tools/codec/response.rs

@@ -144,7 +144,8 @@ pub async fn stream_closed(id: u32, pending: &CursorToolRuntime) -> Result<Optio
         return Ok(None);
     };
     let error = "Cursor Exec stream closed before returning a terminal result";
-    if entry.call.name.eq_ignore_ascii_case("Shell") {
+    if entry.call.name.eq_ignore_ascii_case("Shell") || entry.call.name.eq_ignore_ascii_case("Bash")
+    {
         let command = entry
             .call
             .arguments