Implement new recursive change-count matching algorithm for instance reconciliation

- Introduced a comprehensive rewrite of the matching algorithm, replacing the previous multi-pass approach with a recursive change-count scoring function and greedy assignment strategy.
- Updated the `hydrate.lua` and `matching.lua` files to utilize the new algorithm, enhancing the efficiency of instance matching during hydration.
- Documented the new algorithm's structure, including fast-paths for Ref pins and (Name, ClassName) grouping, which significantly improve matching accuracy and performance.
- Ensured that the new implementation maintains compatibility with existing systems while providing a more robust solution for handling ambiguous instances.

These changes enhance the clarity and efficiency of the reconciliation process, paving the way for improved project management and user experience.

src/snapshot_middleware/dir.rs

@@ -251,11 +251,8 @@ pub fn syncback_dir_no_meta<'sync>(
 
         // Process matched pairs: preserve existing filesystem assignment.
         for (new_ref, old_ref) in &sorted_matched {
-            let (child_snap, _needs_meta, dedup_key) = snapshot.with_joined_path(
-                *new_ref,
-                Some(*old_ref),
-                &taken_names,
-            )?;
+            let (child_snap, _needs_meta, dedup_key) =
+                snapshot.with_joined_path(*new_ref, Some(*old_ref), &taken_names)?;
             taken_names.insert(dedup_key.to_lowercase());
             children.push(child_snap);
         }

src/snapshot_middleware/project.rs

@@ -21,8 +21,8 @@ use crate::{
     },
     snapshot_middleware::Middleware,
     syncback::{
-        filter_properties, inst_path, name_needs_slugify, slugify_name,
-        FsSnapshot, SyncbackReturn, SyncbackSnapshot,
+        filter_properties, inst_path, name_needs_slugify, slugify_name, FsSnapshot, SyncbackReturn,
+        SyncbackSnapshot,
     },
     variant_eq::variant_eq,
     RojoRef,