Centralize project context provided to the assistant (#11471)

This PR restructures the way that tools and attachments add information
about the current project to a conversation with the assistant. Rather
than each tool call or attachment generating a new tool or system
message containing information about the project, they can all
collectively mutate a new type called a `ProjectContext`, which stores
all of the project data that should be sent to the assistant. That data
is then formatted in a single place, and passed to the assistant in one
system message.

This prevents multiple tools/attachments from including redundant
context.

Release Notes:

- N/A

---------

Co-authored-by: Kyle <kylek@zed.dev>

crates/assistant2/src/ui/active_file_button.rs

@@ -1,4 +1,5 @@
-use crate::attachments::{ActiveEditorAttachmentTool, UserAttachmentStore};
+use crate::attachments::ActiveEditorAttachmentTool;
+use assistant_tooling::AttachmentRegistry;
 use editor::Editor;
 use gpui::{prelude::*, Subscription, View};
 use std::sync::Arc;
@@ -13,7 +14,7 @@ enum Status {
 }
 
 pub struct ActiveFileButton {
-    attachment_store: Arc<UserAttachmentStore>,
+    attachment_registry: Arc<AttachmentRegistry>,
     status: Status,
     #[allow(dead_code)]
     workspace_subscription: Subscription,
@@ -21,7 +22,7 @@ pub struct ActiveFileButton {
 
 impl ActiveFileButton {
     pub fn new(
-        attachment_store: Arc<UserAttachmentStore>,
+        attachment_store: Arc<AttachmentRegistry>,
         workspace: View<Workspace>,
         cx: &mut ViewContext<Self>,
     ) -> Self {
@@ -30,14 +31,14 @@ impl ActiveFileButton {
         cx.defer(move |this, cx| this.update_active_buffer(workspace.clone(), cx));
 
         Self {
-            attachment_store,
+            attachment_registry: attachment_store,
             status: Status::NoFile,
             workspace_subscription,
         }
     }
 
     pub fn set_enabled(&mut self, enabled: bool) {
-        self.attachment_store
+        self.attachment_registry
             .set_attachment_tool_enabled::<ActiveEditorAttachmentTool>(enabled);
     }
 
@@ -79,7 +80,7 @@ impl ActiveFileButton {
 impl Render for ActiveFileButton {
     fn render(&mut self, cx: &mut ViewContext<Self>) -> impl IntoElement {
         let is_enabled = self
-            .attachment_store
+            .attachment_registry
             .is_attachment_tool_enabled::<ActiveEditorAttachmentTool>();
 
         let icon = if is_enabled {

crates/assistant2/src/ui/composer.rs

@@ -11,7 +11,7 @@ use ui::{popover_menu, prelude::*, ButtonLike, ContextMenu, Divider, TextSize, T
 #[derive(IntoElement)]
 pub struct Composer {
     editor: View<Editor>,
-    project_index_button: Option<View<ProjectIndexButton>>,
+    project_index_button: View<ProjectIndexButton>,
     active_file_button: Option<View<ActiveFileButton>>,
     model_selector: AnyElement,
 }
@@ -19,7 +19,7 @@ pub struct Composer {
 impl Composer {
     pub fn new(
         editor: View<Editor>,
-        project_index_button: Option<View<ProjectIndexButton>>,
+        project_index_button: View<ProjectIndexButton>,
         active_file_button: Option<View<ActiveFileButton>>,
         model_selector: AnyElement,
     ) -> Self {
@@ -32,11 +32,7 @@ impl Composer {
     }
 
     fn render_tools(&mut self, _cx: &mut WindowContext) -> impl IntoElement {
-        h_flex().children(
-            self.project_index_button
-                .clone()
-                .map(|view| view.into_any_element()),
-        )
+        h_flex().child(self.project_index_button.clone())
     }
 
     fn render_attachment_tools(&mut self, _cx: &mut WindowContext) -> impl IntoElement {