Update single file review docs (#57375)

Release Notes:

- N/A

---------

Co-authored-by: Akrm Al-Hakimi <alk9fh@bosch.com>

crates/settings_content/src/agent.rs

@@ -151,7 +151,7 @@ pub struct AgentSettingsContent {
     pub play_sound_when_agent_done: Option<PlaySoundWhenAgentDone>,
     /// Whether to display agent edits in single-file editors in addition to the review multibuffer pane.
     ///
-    /// Default: true
+    /// Default: false
     pub single_file_review: Option<bool>,
     /// Additional parameters for language model requests. When making a request
     /// to a model, parameters will be taken from the last entry in this list

docs/src/ai/agent-panel.md

@@ -120,9 +120,16 @@ To see which files specifically have been edited, expand the accordion bar that
 
 You can accept or reject each individual change hunk, or the whole set of changes made by the agent.
 
-Edit diffs also appear in singleton buffers.
-If your active tab had edits made by the AI, you'll see diffs with the same accept/reject controls as in the multi-buffer.
-You can turn this off, though, through the `agent.single_file_review` setting.
+Edit diffs can also appear inline in individual files with the same
+keep/reject hunk controls as the multi-buffer review pane. This temporarily overrides the buffer's git diff while review is active. Enable it by setting `agent.single_file_review` to `true` in your settings:
+
+```json
+{
+  "agent": {
+    "single_file_review": true
+  }
+}
+```
 
 ## Terminal Threads {#terminal-threads}