acp: Add support for slash commands (#37304)

Depends on
https://github.com/zed-industries/agent-client-protocol/pull/45

Release Notes:

- N/A

---------

Co-authored-by: Antonio Scandurra <me@as-cii.com>
Co-authored-by: Agus Zubiaga <agus@zed.dev>

crates/acp_thread/src/acp_thread.rs

@@ -785,6 +785,7 @@ pub struct AcpThread {
     session_id: acp::SessionId,
     token_usage: Option<TokenUsage>,
     prompt_capabilities: acp::PromptCapabilities,
+    available_commands: Vec<acp::AvailableCommand>,
     _observe_prompt_capabilities: Task<anyhow::Result<()>>,
     determine_shell: Shared<Task<String>>,
     terminals: HashMap<acp::TerminalId, Entity<Terminal>>,
@@ -858,6 +859,7 @@ impl AcpThread {
         action_log: Entity<ActionLog>,
         session_id: acp::SessionId,
         mut prompt_capabilities_rx: watch::Receiver<acp::PromptCapabilities>,
+        available_commands: Vec<acp::AvailableCommand>,
         cx: &mut Context<Self>,
     ) -> Self {
         let prompt_capabilities = *prompt_capabilities_rx.borrow();
@@ -897,6 +899,7 @@ impl AcpThread {
             session_id,
             token_usage: None,
             prompt_capabilities,
+            available_commands,
             _observe_prompt_capabilities: task,
             terminals: HashMap::default(),
             determine_shell,
@@ -907,6 +910,10 @@ impl AcpThread {
         self.prompt_capabilities
     }
 
+    pub fn available_commands(&self) -> Vec<acp::AvailableCommand> {
+        self.available_commands.clone()
+    }
+
     pub fn connection(&self) -> &Rc<dyn AgentConnection> {
         &self.connection
     }
@@ -2864,6 +2871,7 @@ mod tests {
                         audio: true,
                         embedded_context: true,
                     }),
+                    vec![],
                     cx,
                 )
             });

crates/acp_thread/src/connection.rs

@@ -75,7 +75,6 @@ pub trait AgentConnection {
     fn telemetry(&self) -> Option<Rc<dyn AgentTelemetry>> {
         None
     }
-
     fn into_any(self: Rc<Self>) -> Rc<dyn Any>;
 }
 
@@ -339,6 +338,7 @@ mod test_support {
                         audio: true,
                         embedded_context: true,
                     }),
+                    vec![],
                     cx,
                 )
             });