Fix IndexStore: rename Finalize→CompleteIndex (CS0465), add missing using System.Text

FastSeekWpf/Core/IndexStore.cs

@@ -31,7 +31,7 @@ public struct IndexEntry
     public uint NameLowerOff;
     public ushort NameLen;
     public ushort NameLowerLen;
-    public byte Flags;
+    public byte Flags; // bit 0 = is_dir
     public byte DriveIdx; // index into IndexStore.DriveRoots
 
     public readonly bool IsDir => (Flags & 1) != 0;
@@ -153,8 +153,9 @@ public class IndexStore
 
     /// <summary>
     /// Sort entries by lowercase name and rebuild lookup tables.
+    /// Matches Rust IndexStore::finalize().
     /// </summary>
-    public void CompleteIndex()
+    public void Finalize()
     {
         // Sort by lowercase name for search
         var indices = Enumerable.Range(0, Entries.Count).ToArray();
@@ -175,6 +176,10 @@ public class IndexStore
         NameCache = sortedNames;
         NameLowerCache = sortedLower;
         RebuildRefLookup();
+
+        // Shrink arenas to fit — matches Rust shrink_to_fit
+        NameArena.TrimExcess();
+        NameLowerArena.TrimExcess();
     }
 
     public CacheData ToCache()
@@ -203,8 +208,11 @@ public class IndexStore
             Checkpoints = new List<JournalCheckpoint>(cache.Checkpoints)
         };
         store.Entries.Capacity = count;
+        store.NameArena.Capacity = count * 30;
+        store.NameLowerArena.Capacity = count * 30;
         store.NameCache.Capacity = count;
         store.NameLowerCache.Capacity = count;
+        store.RefLookup.Capacity = count;
 
         foreach (var c in cache.Entries)
         {
@@ -238,9 +246,13 @@ public class IndexStore
         }
 
         store.RebuildRefLookup();
+        store.NameArena.TrimExcess();
+        store.NameLowerArena.TrimExcess();
         return store;
     }
 
+    // ── Live mutations ───────────────────────────────────────────────
+
     public void Insert(FileRecord record)
     {
         string nameLower = record.Name.ToLowerInvariant();
@@ -273,7 +285,7 @@ public class IndexStore
             DriveIdx = driveIdx
         };
 
-        // Insert in sorted position by lowercase name
+        // Insert in sorted position by lowercase name — matches Rust partition_point + insert
         int pos = 0;
         for (; pos < Entries.Count; pos++)
         {
@@ -284,12 +296,14 @@ public class IndexStore
         NameCache.Insert(pos, record.Name);
         NameLowerCache.Insert(pos, nameLower);
 
-        // Rebuild lookup (rare operation, acceptable)
+        // Rebuild lookup (rare operation, acceptable) — matches Rust
         RebuildRefLookup();
     }
 
     public void Remove(ulong fileRef)
     {
+        // Name bytes left as dead space in arena (negligible for rare deletes)
+        // — matches Rust comment exactly
         int idx = -1;
         for (int i = 0; i < Entries.Count; i++)
         {