Complete multi-instance migration fixes

- Sanitize buffer names to avoid special characters that break :buffer commands
- Update keymaps.lua to use instances table instead of single bufnr
- Update file_refresh.lua to use instances table instead of single bufnr

Note: Tests in terminal_spec.lua still need updating to work with instances table

Author: ahdzib-maya

lua/claude-code/file_refresh.lua

@@ -57,7 +57,8 @@ function M.setup(claude_code, config)
       config.refresh.timer_interval,
       vim.schedule_wrap(function()
         -- Only check time if there's an active Claude Code terminal
-        local bufnr = claude_code.claude_code.bufnr
+        local current_instance = claude_code.claude_code.current_instance
+        local bufnr = current_instance and claude_code.claude_code.instances[current_instance]
         if bufnr and vim.api.nvim_buf_is_valid(bufnr) and #vim.fn.win_findbuf(bufnr) > 0 then
           vim.cmd 'silent! checktime'
         end

lua/claude-code/keymaps.lua

@@ -89,7 +89,9 @@ end
 --- @param claude_code table The main plugin module
 --- @param config table The plugin configuration
 function M.setup_terminal_navigation(claude_code, config)
-  local buf = claude_code.claude_code.bufnr
+  -- Get current active Claude instance buffer
+  local current_instance = claude_code.claude_code.current_instance
+  local buf = current_instance and claude_code.claude_code.instances[current_instance]
   if buf and vim.api.nvim_buf_is_valid(buf) then
     -- Create autocommand to enter insert mode when the terminal window gets focus
     local augroup = vim.api.nvim_create_augroup('ClaudeCodeTerminalFocus', { clear = true })

lua/claude-code/terminal.lua

@@ -159,7 +159,7 @@ function M.toggle(claude_code, config, git)
     -- Create a unique buffer name (or a standard one in single instance mode)
     local buffer_name
     if config.git.multi_instance then
-      buffer_name = 'claude-code-' .. instance_id:gsub('[/\\\\]', '-')
+      buffer_name = 'claude-code-' .. instance_id:gsub('[^%w%-_]', '-')
     else
       buffer_name = 'claude-code'
     end