Truncate line when accepting inline suggestions for Supermaven (#13884)

Configures inline completions to delete the remaining text on the given
line. This doesn't affect the github copilot inline completion provider
since it seems to only generate suggestions if the cursor is at the end
of the line but fixes the usability issues related to Supermaven.




https://github.com/user-attachments/assets/1b8bc9a3-4666-4665-a436-96e4beee01bb





Release Notes:

- Fixed https://github.com/zed-industries/zed/issues/13039

---------

Co-authored-by: Antonio Scandurra <me@as-cii.com>
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

crates/copilot/src/copilot_completion_provider.rs

@@ -8,7 +8,7 @@ use language::{
     Buffer, OffsetRangeExt, ToOffset,
 };
 use settings::Settings;
-use std::{path::Path, sync::Arc, time::Duration};
+use std::{ops::Range, path::Path, sync::Arc, time::Duration};
 
 pub const COPILOT_DEBOUNCE_TIMEOUT: Duration = Duration::from_millis(75);
 
@@ -239,7 +239,7 @@ impl InlineCompletionProvider for CopilotCompletionProvider {
         buffer: &Model<Buffer>,
         cursor_position: language::Anchor,
         cx: &'a AppContext,
-    ) -> Option<&'a str> {
+    ) -> Option<(&'a str, Option<Range<language::Anchor>>)> {
         let buffer_id = buffer.entity_id();
         let buffer = buffer.read(cx);
         let completion = self.active_completion()?;
@@ -269,7 +269,7 @@ impl InlineCompletionProvider for CopilotCompletionProvider {
             if completion_text.trim().is_empty() {
                 None
             } else {
-                Some(completion_text)
+                Some((completion_text, None))
             }
         } else {
             None