Closes#1981
@file references and /skill commands become inline tags anywhere in the prompt, in Home and in a conversation. Tags are edited as a unit (Backspace/Delete, arrows) and are not committed mid-IME composition. Files and folders dragged from the Project view become references, mapped into the task worktree; paths outside the project, traversal and relative paths are rejected, and a deleted reference can be dropped again.
Co-authored-by: panda-student <71381346+panda-student@users.noreply.github.com>
