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/diff.rs

@@ -780,6 +780,7 @@ fn choose_pair(editor: &mut Editor) -> u64 {
 
 fn comparison() -> Comparison {
     Comparison {
+        blame: Default::default(),
         revisions: ["abcdef123".into(), "working:snapshot".into()],
         before: "abcdef123".into(),
         after: "Working checkout".into(),
@@ -1774,6 +1775,7 @@ fn jujutsu_categories_empty_comparison_and_command_mode_entry_are_complete() {
     assert!(editor.apply_diff_result(
         id,
         Ok(Outcome::Comparison(Comparison {
+            blame: Default::default(),
             revisions: ["working:snapshot".into(), "working:snapshot".into()],
             before: "Working".into(),
             after: "Working".into(),
@@ -1806,6 +1808,7 @@ fn live_state(before: Vec<String>, after: Vec<String>, eof: bool) -> DiffState {
         Category::Commits,
     ));
     state.comparison = Some(Comparison {
+        blame: Default::default(),
         revisions: ["base".into(), "working:snapshot".into()],
         root: PathBuf::new(),
         before: "base".into(),