fix: support large files in comparisons

Replace the 16 MiB comparison rejection with independent bounded per-side loading and frozen Working blobs. Bound diff computation, defer large inline highlighting, index source-row navigation, and expose actual load failures. Verified the real 52.3 MB parser through repository/session APIs and terminal rendering with EOF/start navigation.

tests/unit/tui.rs

@@ -4612,6 +4612,68 @@ fn hiding_diff_explorer_reclaims_workspace_and_restores_its_geometry() {
     assert_eq!(panels.files.unwrap().0, original[0].0);
 }
 
+#[test]
+fn unavailable_file_documents_show_the_actual_error_in_managed_workspaces() {
+    let mut file = deletion_file();
+    file.loaded = false;
+    let mut diff = diff_comparison(vec![file]);
+    diff.loading = false;
+    diff.error = Some("parser.c exceeds 128 MiB file limit".into());
+    let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(80, 12)).unwrap();
+    let mut panels = WheelPanels {
+        workspace_managed: true,
+        ..WheelPanels::default()
+    };
+    terminal
+        .draw(|frame| {
+            panels.draw_documents(frame, &diff, frame.area(), None, None);
+        })
+        .unwrap();
+    let text = screen_text(&terminal);
+    assert!(text.contains("parser.c exceeds 128 MiB file limit"));
+    assert!(!text.contains("select the file to retry"));
+}
+
+#[test]
+fn large_generated_additions_render_first_scroll_and_final_rows_without_reparsing() {
+    let after = (0..25_000)
+        .map(|row| format!("state_row_{row:05} = 1234567890123456789012345678901234567890;"))
+        .collect::<Vec<_>>();
+    let hunks = crate::diff::line_hunks(&[], false, &after, true);
+    let mut diff = diff_comparison(vec![ChangedFile {
+        path: "parser.c".into(),
+        old_path: None,
+        status: FileStatus::Added,
+        loaded: true,
+        before: Vec::new(),
+        after,
+        before_eof: false,
+        after_eof: true,
+        hunks,
+        notice: None,
+    }]);
+    diff.files_visible = false;
+    diff.focus = Focus::After;
+    let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(100, 12)).unwrap();
+    let mut panels = WheelPanels::default();
+    let mut counts = None;
+    for row in [0, 3, 12_500, 24_999] {
+        diff.reveal_source_row(Focus::After, row);
+        render_diff(&mut terminal, &diff, &mut panels);
+        assert!(screen_text(&terminal).contains(&format!("state_row_{row:05}")));
+        let syntax = panels.diff_syntax.as_ref().unwrap();
+        assert_eq!(
+            *counts.get_or_insert(syntax.after.parse_counts()),
+            syntax.after.parse_counts()
+        );
+        assert!(syntax.after.error().is_some());
+        assert_eq!(
+            diff.comparison.as_ref().unwrap().files[0].after.len(),
+            25_000
+        );
+    }
+}
+
 #[test]
 fn diff_notices_empty_comparisons_and_tiny_layouts_remain_renderable() {
     let mut terminal = Terminal::new(ratatui::backend::TestBackend::new(100, 12)).unwrap();