Add support for the "..." entry in file_scan_inclusions (#64440)

## Objective

Let projects add inclusion patterns without repeating defaults or
patterns inherited from user settings.

Part of #64399.

## Solution

Extend the `"..."` behavior from #62769 and #64222 to
`file_scan_inclusions` using the shared merge implementation. `"..."`
includes the resolved inherited list, omitting it replaces the list, and
`[]` clears it. Duplicate entries retain their first occurrence.

Stop importing VS Code’s `files.watcherInclude` as inclusion patterns
because it configures additional watch roots rather than overriding Git
ignores.

## Testing

Tested on macOS with settings merge, VS Code import, and worktree
integration tests. Coverage includes preservation of the `.env*`
default, layered inheritance, replacement, clearing, and deduplication.
The worktree test verifies that inherited and project-specific patterns
include Git-ignored files while exclusions still take precedence.

To check manually, configure different user and project inclusion
patterns and add ignored files matching each. Include `"..."` to retain
inherited patterns, then repeat without it and with `[]` to verify
replacement and clearing. Confirm that excluded files remain absent.

## Self-Review Checklist:

- [x] I’ve reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content adheres to Zed’s UI standards
([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
and
[icon](https://github.com/zed-industries/zed/blob/main/crates/icons/README.md)
guidelines)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

---

Release Notes:

- Added support for `"..."` in `file_scan_inclusions` so project
settings can extend inherited inclusion patterns.

crates/settings/src/vscode_import.rs

@@ -1136,15 +1136,8 @@ impl VsCodeSettings {
                 })
                 .filter(|r| !r.is_empty())
                 .map(SplicingVec::from),
-            file_scan_inclusions: self
-                .read_value("files.watcherInclude")
-                .and_then(|v| v.as_array())
-                .map(|v| {
-                    v.iter()
-                        .filter_map(|n| n.as_str().map(str::to_owned))
-                        .collect::<Vec<_>>()
-                })
-                .filter(|r| !r.is_empty()),
+            // `files.watcherInclude` adds watch roots, not Git-ignore overrides
+            file_scan_inclusions: None,
             scan_symlinks: None,
             private_files: None,
             hidden_files: None,
@@ -1243,6 +1236,46 @@ mod tests {
             .reduce_motion
     }
 
+    #[test]
+    fn test_import_watcher_include_preserves_file_scan_inclusions() -> Result<()> {
+        let inherited = WorktreeSettingsContent {
+            file_scan_inclusions: Some(SplicingVec::from(vec![
+                ".env*".to_string(),
+                "**/*.local".to_string(),
+            ])),
+            ..Default::default()
+        };
+        for content in [
+            r#"{}"#,
+            r#"{"files.watcherInclude": []}"#,
+            r#"{"files.watcherInclude": ["linked-folder"]}"#,
+            r#"{"files.watcherInclude": ["..."]}"#,
+            r#"{"files.watcherInclude": ["linked-folder", false]}"#,
+            r#"{"files.watcherInclude": {"linked-folder": true}}"#,
+        ] {
+            let mut content: Value = serde_json::from_str(content)?;
+            content["editor.tabSize"] = serde_json::json!(8);
+            let imported = VsCodeSettings::from_str(
+                &serde_json::to_string(&content)?,
+                VsCodeSettingsSource::VsCode,
+            )?
+            .settings_content();
+            assert_eq!(imported.project.worktree.file_scan_inclusions, None);
+            assert_eq!(
+                imported.project.all_languages.defaults.tab_size,
+                NonZeroU32::new(8)
+            );
+
+            let mut unchanged = inherited.clone();
+            unchanged.merge_from(&imported.project.worktree);
+            assert_eq!(
+                unchanged.file_scan_inclusions,
+                inherited.file_scan_inclusions
+            );
+        }
+        Ok(())
+    }
+
     #[test]
     fn test_import_read_only_files() -> Result<()> {
         let inherited = WorktreeSettingsContent {