assistant2: Allow creating agent profiles via settings (#27216)

This PR adds support for creating new agent profiles via the settings:

```json
{
  "assistant": {
    "profiles": {
      "lua": {
        "name": "Lua",
        "tools": {
          "lua-interpreter": true
        }
      },
      "lua-thinking": {
        "name": "Lua + Thinking",
        "tools": {
          "lua-interpreter": true,
          "thinking": true
        }
      }
    }
  }
}
```

Release Notes:

- N/A

crates/assistant_settings/src/agent_profile.rs

@@ -0,0 +1,59 @@
+use std::sync::Arc;
+
+use collections::HashMap;
+use gpui::SharedString;
+
+/// A profile for the Zed Agent that controls its behavior.
+#[derive(Debug, Clone)]
+pub struct AgentProfile {
+    /// The name of the profile.
+    pub name: SharedString,
+    pub tools: HashMap<Arc<str>, bool>,
+    #[allow(dead_code)]
+    pub context_servers: HashMap<Arc<str>, ContextServerPreset>,
+}
+
+#[derive(Debug, Clone)]
+pub struct ContextServerPreset {
+    #[allow(dead_code)]
+    pub tools: HashMap<Arc<str>, bool>,
+}
+
+impl AgentProfile {
+    pub fn read_only() -> Self {
+        Self {
+            name: "Read-only".into(),
+            tools: HashMap::from_iter([
+                ("diagnostics".into(), true),
+                ("fetch".into(), true),
+                ("list-directory".into(), true),
+                ("now".into(), true),
+                ("path-search".into(), true),
+                ("read-file".into(), true),
+                ("regex-search".into(), true),
+                ("thinking".into(), true),
+            ]),
+            context_servers: HashMap::default(),
+        }
+    }
+
+    pub fn code_writer() -> Self {
+        Self {
+            name: "Code Writer".into(),
+            tools: HashMap::from_iter([
+                ("bash".into(), true),
+                ("delete-path".into(), true),
+                ("diagnostics".into(), true),
+                ("edit-files".into(), true),
+                ("fetch".into(), true),
+                ("list-directory".into(), true),
+                ("now".into(), true),
+                ("path-search".into(), true),
+                ("read-file".into(), true),
+                ("regex-search".into(), true),
+                ("thinking".into(), true),
+            ]),
+            context_servers: HashMap::default(),
+        }
+    }
+}