fix: defer auto_start_watch_mode callback to prevent split blocking

[dmmulroy]

Summary

• Wraps M.run() in vim.schedule() in the auto_start_watch_mode autocommand callback
• Allows buffer/window operations to complete before notifications start

Problem

When auto_start_watch_mode = true, opening files with vertical split from nvim-tree or telescope failed on first attempt but worked on second.

Root cause: The BufRead/BufNewFile autocommand called M.run() synchronously during buffer load. The immediate vim.notify() call created floating windows that interfered with split operations in progress.

Second attempt worked because M.run() short-circuits when process already running (no notifications created).

Fix

Defer M.run() to next event loop iteration with vim.schedule(), allowing split to complete first.

Closes #75