fix(formatter): Handle THEN on separate line and multi-line conditions

- Track when IF has THEN on separate line
- Don't increase indent after IF until THEN is seen
- Increase indent after THEN for content
- Continuation lines in conditions stay at same level as IF
- END_IF stays at same level as content (TIA Portal style)

src/formatter.lua

@@ -67,6 +67,7 @@ function M.format_document(content, options)
   local in_var_section = false
   local in_code_section = false
   local prev_line_keyword = nil
+  local prev_line_had_then = true  -- Track if previous line had THEN
   
   -- FB call continuation tracking
   local in_fb_call = false
@@ -300,6 +301,11 @@ function M.format_document(content, options)
         indent_level = indent_level + 1
       -- Check for same-level keywords (THEN, ELSE, DO, OF on their own line)
       elseif same_level_keywords[kw] then
+        -- For THEN on its own line (after IF without THEN on same line), increase indent for content
+        if kw == "THEN" then
+          -- Increase indent after THEN for content
+          indent_level = indent_level + 1
+        end
         -- For ELSIF and ELSE, reset to IF base level
         if (kw == "ELSIF" or kw == "ELSE") and if_base_level then
           indent_level = if_base_level
@@ -311,12 +317,28 @@ function M.format_document(content, options)
         end
       -- Check for block starters
       elseif is_block_starter(kw) then
-        -- Save base level for IF statements
+        -- Save base level for IF statements AFTER checking for THEN
         if kw == "IF" then
-          if_base_level = indent_level
+          -- Check if THEN is on the same line
+          if trimmed:match("THEN%s*$") then
+            if_base_level = indent_level
+            prev_line_had_then = true
+            indent_level = indent_level + 1
+          else
+            -- THEN on separate line, don't increase yet
+            if_base_level = indent_level
+            prev_line_had_then = false
+          end
+        elseif kw == "THEN" then
+          -- THEN on its own line, increase for content
+          prev_line_had_then = true
+          indent_level = indent_level + 1
+        else
+          -- For other block starters (FOR, WHILE, REGION, CASE), always increase
+          prev_line_had_then = true
+          indent_level = indent_level + 1
         end
         table.insert(formatted_lines, formatted_line)
-        indent_level = indent_level + 1
       -- Regular line
       else
         if needs_semicolon(trimmed) and not in_fb_call then
@@ -327,6 +349,10 @@ function M.format_document(content, options)
     end
 
     prev_line_keyword = kw
+    -- Reset THEN tracking for next iteration (unless current line has THEN)
+    if kw ~= "THEN" then
+      prev_line_had_then = true
+    end
   end
 
   local result = table.concat(formatted_lines, "\n")