assistant2: Wire up context picker with inline assist (#22106)

This PR wire up the context picker with the inline assist.

UI is not finalized.

Release Notes:

- N/A

---------

Co-authored-by: Richard <richard@zed.dev>
Co-authored-by: Agus <agus@zed.dev>

crates/assistant2/src/context_store.rs

@@ -0,0 +1,47 @@
+use gpui::SharedString;
+
+use crate::context::{Context, ContextId, ContextKind};
+
+pub struct ContextStore {
+    context: Vec<Context>,
+    next_context_id: ContextId,
+}
+
+impl ContextStore {
+    pub fn new() -> Self {
+        Self {
+            context: Vec::new(),
+            next_context_id: ContextId(0),
+        }
+    }
+
+    pub fn context(&self) -> &Vec<Context> {
+        &self.context
+    }
+
+    pub fn drain(&mut self) -> Vec<Context> {
+        self.context.drain(..).collect()
+    }
+
+    pub fn clear(&mut self) {
+        self.context.clear();
+    }
+
+    pub fn insert_context(
+        &mut self,
+        kind: ContextKind,
+        name: impl Into<SharedString>,
+        text: impl Into<SharedString>,
+    ) {
+        self.context.push(Context {
+            id: self.next_context_id.post_inc(),
+            name: name.into(),
+            kind,
+            text: text.into(),
+        });
+    }
+
+    pub fn remove_context(&mut self, id: &ContextId) {
+        self.context.retain(|context| context.id != *id);
+    }
+}