fix: show revision-aware blame in diff buffers

Diff and snapshot sources were excluded before scheduling, and the separate diff renderer never painted attribution. Capture per-side Git provenance, preserve private object stores for historical tabs, and reuse the current-line worker and cache.

tests/unit/editor.rs

@@ -1879,6 +1879,7 @@ fn hidden_tab_diff_results_restore_visible_insert_interaction_and_route_request_
     assert!(editor.apply_diff_result(
         comparison_request,
         Ok(Outcome::Comparison(Comparison {
+            blame: Default::default(),
             root: editor.project_root().to_owned(),
             revisions: ["base".into(), "working-snapshot".into()],
             before: "base".into(),
@@ -3068,6 +3069,7 @@ fn working_diff(editor: &mut Editor, root: &Path, paths: &[&str]) -> Box<[(PathB
     assert!(editor.apply_diff_result(
         id,
         Ok(Outcome::Comparison(Comparison {
+            blame: Default::default(),
             root: root.canonicalize().unwrap(),
             revisions: ["base".into(), "working-snapshot".into()],
             before: "base".into(),
@@ -3105,6 +3107,7 @@ fn historical_diff(editor: &mut Editor, root: &Path, before: Vec<String>, after:
     editor.apply_diff_result(
         id,
         Ok(Outcome::Comparison(Comparison {
+            blame: Default::default(),
             root: root.to_owned(),
             revisions: ["base".into(), "head".into()],
             before: "base".into(),
@@ -4108,6 +4111,7 @@ fn bookmark_refresh_reloads_paths_and_preserves_view_until_lazy_content_arrives(
     assert!(editor.apply_diff_result(
         refresh,
         Ok(Outcome::BookmarkRefresh(Comparison {
+            blame: Default::default(),
             root: directory.0.clone(),
             revisions: ["base".into(), "topic-snapshot".into()],
             before: "base".into(),
@@ -4229,6 +4233,7 @@ fn completed_working_refresh_serializes_lazy_selection_and_invalidates_pending_n
         let loaded_after = target.after.clone();
         target.loaded = false;
         let replacement = crate::diff::Comparison {
+            blame: Default::default(),
             root: directory.0.clone(),
             revisions: ["base".into(), "ahead-snapshot".into()],
             before: "base".into(),