fix(vim.hl): range(0,…) highlight not cleared after buffer-switch #40130

Problem:
When `vim.hl.range(0, …, { timeout = N })` is called, the deferred
`range_hl_clear` captures `buf=0`, which resolves to an arbitrary
"current buffer" at timeout. This may cause a stale highlight that never
gets cleared.

Solution:
Resolve `buf=0` explicitly, before `range_hl_clear` captures it.

runtime/lua/vim/hl.lua

@@ -50,6 +50,8 @@ M.priorities = {
 --- @return fun()? range_clear A function which allows clearing the highlight manually.
 --- nil is returned if timeout is not specified
 function M.range(buf, ns, higroup, start, finish, opts)
+  -- Resolve buf=0 so the deferred `range_hl_clear` works correctly even after buffer-switch.
+  buf = vim._resolve_bufnr(buf)
   opts = opts or {}
   local regtype = opts.regtype or 'v'
   local inclusive = opts.inclusive or false