feat: add agent mode and CoderType command for mode switching

- Add agent module with tool execution support (read_file, edit_file, bash)
- Add agent/ui.lua with chat sidebar, input area, and real-time logs panel
- Add agent/logs.lua for token counting and request/response logging
- Add generate_with_tools to claude.lua and ollama.lua for tool use
- Add chat_switcher.lua modal picker for Ask/Agent mode selection
- Add CoderType command to show mode switcher (replaces C-Tab keymaps)
- Update ask.lua and agent/ui.lua headers to reference :CoderType

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

.gitignore

@@ -1,7 +1,48 @@
 # Codetyper.nvim - AI coding partner files
 *.coder.*
 .coder/
+.claude/
 
-/@
-add gitignore for lua files
-/@
+# Created by https://www.toptal.com/developers/gitignore/api/lua
+
+### Lua ###
+# Compiled Lua sources
+luac.out
+
+# luarocks build files
+*.src.rock
+*.zip
+*.tar.gz
+
+# Object files
+*.o
+*.os
+*.ko
+*.obj
+*.elf
+
+# Precompiled Headers
+*.gch
+*.pch
+
+# Libraries
+*.lib
+*.a
+*.la
+*.lo
+*.def
+*.exp
+
+# Shared objects (inc. Windows DLLs)
+*.dll
+*.so
+*.so.*
+*.dylib
+
+# Executables
+*.exe
+*.out
+*.app
+*.i*86
+*.x86_64
+*.hex