fix: add missing oil.nvim filetype checks for window selection

- Add oil filetype check in diff.lua's _find_main_editor_window()
- Add oil filetype check in open_file.lua's find_main_editor_window()
- Add oil filetype check in init.lua's ClaudeCodeSend command

These changes ensure oil.nvim buffers are properly excluded when
searching for main editor windows, preventing diff views and file
opens from appearing in the oil explorer window.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

lua/claudecode/diff.lua

@@ -49,6 +49,7 @@ function M._find_main_editor_window()
         or filetype == "neo-tree-popup"
         or filetype == "ClaudeCode"
         or filetype == "NvimTree"
+        or filetype == "oil"
         or filetype == "aerial"
         or filetype == "tagbar"
       )

lua/claudecode/init.lua

@@ -408,6 +408,7 @@ function M._create_commands()
 
     local is_tree_buffer = current_ft == "NvimTree"
       or current_ft == "neo-tree"
+      or current_ft == "oil"
       or string.match(current_bufname, "neo%-tree")
       or string.match(current_bufname, "NvimTree")
 

lua/claudecode/tools/open_file.lua

@@ -75,6 +75,7 @@ local function find_main_editor_window()
         or filetype == "neo-tree-popup"
         or filetype == "ClaudeCode"
         or filetype == "NvimTree"
+        or filetype == "oil"
         or filetype == "aerial"
         or filetype == "tagbar"
       )