Fallback should use <Tab> instead of tab character when accept_fallback is nil

[Jonkimi]

Problem

In lua/codeium/virtual_text.lua

windsurf.nvim/lua/codeium/virtual_text.lua

Line 140 in 821b570

local default = config.options.virtual_text.accept_fallback or (vim.fn.pumvisible() == 1 and "<C-N>" or "\t")

, when config.options.virtual_text.accept_fallback is nil and there is no completion menu (pumvisible() == 0), the current fallback behavior inserts a tab character ("\t"). This is usually not the expected Vim behavior, since users typically expect <Tab> to trigger mappings or plugin logic, not insert a literal tab character. This can lead to unexpected editing outcomes and breaks common insert mode workflows, especially when <Tab> is remapped for completion or snippet expansion.

How to Reproduce

1. In your Neovim config, explicitly disable windsurf/codeium with:

   -- disable codeium by default
   require("codeium").disable()

2. Open any file for editing.
3. Enter insert mode and press Tab.

Result:
You will encounter the error described in #294:

E5108: Error executing lua: ...local/share/nvim2/lazy/nvim-cmp/lua/cmp/utils/keymap.lua:273: "replace_keycodes" requires "expr"

This happens because the fallback returns a tab character ("\t") rather than properly simulating a <Tab> key event, breaking expected plugin and mapping logic.

Proposed Solution

Change the fallback logic so that when accept_fallback is nil, and the completion menu is not visible, fallback returns "<Tab>" instead of "\t". This ensures the correct Vim key event is triggered, supporting user mappings and plugin behaviors as intended.

Relevant Code

local default = config.options.virtual_text.accept_fallback or (vim.fn.pumvisible() == 1 and "<C-N>" or "\t")

Should be updated to:

local default = config.options.virtual_text.accept_fallback or (vim.fn.pumvisible() == 1 and "<C-N>" or "<Tab>")