feat: add selective line restoration from historical commits

Add a new Tauri command to produce a diff between the working file and a historical commit (get_file_restore_patch) and support a new apply action ("restore-lines") that validates and applies only text-line changes for a single regular file.

Behavior changes and constraints:
- Fetch a filtered reverse diff for a file in a commit so UI can display selectable lines from an older revision.
- Applying "restore-lines" verifies the target is a regular file, rejects binary/metadata patches, and ensures the patch only modifies the selected file.
- Restored lines are applied to the working tree without staging other changes; the index is preserved.
- The operation rejects stale patches or patches targeting the wrong file.

UI wiring:
- Compare dialog gets a "Restore lines…" action for applicable modified files and opens the line-patch dialog in restore mode.
- Line-patch dialog gains a restore mode (restoreCommit) with adjusted UI/rendering to pair removed/added lines, helper text, and dedicated "Restore selected" / "Restore hunk" actions.
- App integration handles fetching the restore patch, applying selected lines, and refreshing views.

Tests:
- Add tests covering correct behavior (preserve unstaged/staged changes and index) and guard cases (stale/wrong-file patches).

src-tauri/src/main.rs

@@ -19,7 +19,7 @@ use git::{
     compare_file_to_parent, create_branch, create_tag, cred_delete, cred_load, cred_save,
     delete_branch, delete_commit_note, delete_remote_branch, delete_remote_branches, delete_tag,
     diff_file_against_working_tree, fetch, fetch_commit_notes, get_bisect_state, get_commit_note,
-    get_file_blame, get_file_patch, get_remote_url, get_status, git_lfs_install, git_lfs_prune,
+    get_file_blame, get_file_patch, get_file_restore_patch, get_remote_url, get_status, git_lfs_install, git_lfs_prune,
     git_lfs_pull, git_lfs_status, git_lfs_track, git_lfs_untrack, init_repository,
     last_commit_message, list_branches, list_commits, list_file_history,
     list_interactive_rebase_commits, list_reflog, list_remotes, list_repository_files,
@@ -392,6 +392,7 @@ async fn main() {
             stash_drop,
             restore_files,
             get_file_patch,
+            get_file_restore_patch,
             apply_file_patch,
             commit,
             amend_commit,