Backticked strings getting unexpectedly executed as external commands

Describe the bug

According to the docs "Working with strings", backticks are one of the ways to create a string. Let's try:

~: let a = "hello" + "world" ; $a
helloworld
~: let a = "hello" + `world` ; $a
helloworld
~: let a = `hello` + "world" ; $a
Error: nu::shell::external_command

  × External command failed
   ╭─[entry #32:1:1]
 1 │ let a = `hello` + "world" ; $a
   ·         ───┬───
   ·            ╰── executable was not found
   ╰────
  help: No such file or directory (os error 2)

This can lead to counter-intuitive things like:

$ cat ~/bin/wipeeverything
#!/usr/bin/env bash
#rm -rf /
echo "Wiping everything"

$ cat supertool.nu
let messages = [`hello` `world`] # creating strings
let message = `wipeeverything` # creating string (big mistake)
let combined = $messages | append $message
$combined

$ nu supertool.nu
╭───┬───────────────────╮
│ 0 │ hello             │
│ 1 │ world             │
│ 2 │ Wiping everything │
╰───┴───────────────────╯

How to reproduce

See description.

Expected behavior

If it's one of the ways to create strings, then it should behave like all other strings. If let a = "hello" + "world" doesn't run the hello executable, then neither should let a = `hello` + "world".

Screenshots

No response

Configuration

Additional context

No response

Reproduce the behavior from the issue using nu supertool.nu and the backtick examples, then read the documented “Working with strings” behavior alongside the command execution path. Done means backticked values in concatenations and lists remain strings and do not execute matching external commands, while the existing string examples continue to work.