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.

src/diff.rs

@@ -4,6 +4,7 @@ use std::{
     borrow::Cow,
     collections::{BTreeMap, BTreeSet},
     path::{Path, PathBuf},
+    sync::Arc,
     time::{Duration, Instant},
 };
 use unicode_segmentation::UnicodeSegmentation;
@@ -141,10 +142,19 @@ pub struct ChangedFile {
     pub hunks: Vec<Hunk>,
     pub notice: Option<String>,
 }
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub struct BlameRevision {
+    pub store: PathBuf,
+    pub commit: String,
+    pub(crate) keepalive: Option<Arc<crate::repository::Temporary>>,
+}
+
 #[derive(Debug)]
 pub struct Comparison {
     /// Immutable comparison-context IDs; captured review text also freezes live edits.
     pub revisions: [String; 2],
+    /// Git object stores and immutable attribution baselines for Before/After.
+    pub blame: [Option<BlameRevision>; 2],
     pub before: String,
     pub after: String,
     pub files: Vec<ChangedFile>,
@@ -670,6 +680,7 @@ impl DiffState {
     pub(crate) fn set_resolver_paths(&mut self, root: PathBuf, paths: Vec<PathBuf>, file: usize) {
         let comparison = self.comparison.get_or_insert_with(|| Comparison {
             revisions: Default::default(),
+            blame: Default::default(),
             before: "Resolution".into(),
             after: "Other version".into(),
             files: Vec::new(),