refactor: optimize file list processing order

Move file list chunking before content processing to ensure consistent
ordering of operations and improve code flow. Also increase TOP_RELATED
constant from 20 to 25 for better related files detection.

The chunking logic now runs first, followed by optional content processing,
which makes the code more maintainable and logical in its execution order.

lua/CopilotChat/context.lua

@@ -65,7 +65,7 @@ local OFF_SIDE_RULE_LANGUAGES = {
 }
 
 local TOP_SYMBOLS = 100
-local TOP_RELATED = 20
+local TOP_RELATED = 25
 local MULTI_FILE_THRESHOLD = 5
 
 --- Compute the cosine similarity between two vectors
@@ -324,6 +324,24 @@ function M.files(winnr, with_content)
 
   local out = {}
 
+  -- Create file list in chunks
+  local chunk_size = 100
+  for i = 1, #files, chunk_size do
+    local chunk = {}
+    for j = i, math.min(i + chunk_size - 1, #files) do
+      table.insert(chunk, files[j])
+    end
+
+    local chunk_number = math.floor(i / chunk_size)
+    local chunk_name = chunk_number == 0 and 'file_map' or 'file_map' .. tostring(chunk_number)
+
+    table.insert(out, {
+      content = table.concat(chunk, '\n'),
+      filename = chunk_name,
+      filetype = 'text',
+    })
+  end
+
   -- Read all files if we want content as well
   if with_content then
     async.util.scheduler()
@@ -346,26 +364,6 @@ function M.files(winnr, with_content)
         table.insert(out, file_data)
       end
     end
-
-    return out
-  end
-
-  -- Create file list in chunks
-  local chunk_size = 100
-  for i = 1, #files, chunk_size do
-    local chunk = {}
-    for j = i, math.min(i + chunk_size - 1, #files) do
-      table.insert(chunk, files[j])
-    end
-
-    local chunk_number = math.floor(i / chunk_size)
-    local chunk_name = chunk_number == 0 and 'file_map' or 'file_map' .. tostring(chunk_number)
-
-    table.insert(out, {
-      content = table.concat(chunk, '\n'),
-      filename = chunk_name,
-      filetype = 'text',
-    })
   end
 
   return out