Better error message when serving with both hot patch and release flags

when i run the following command with web platform
`dx serve --hotpatch --release`
i get the error message:

> [dev] Build failed: Failed to read file: No such file or directory (os error 2)
> 1: No such file or directory (os error 2)

when i run:
`dx serve --release`
everyhing works file

it would be nice to show error message that says something like:

> do not use hotpatch in release mode

instead of file not found error (won't show file name too) or dx itself disable hotpath under the hood and show warning

Start by reproducing `dx serve --hotpatch --release` and compare its output with `dx serve --release`. Trace the `dx serve` handling for the `--hotpatch` and `--release` flags; done means the incompatible combination produces a clear error or warning instead of the file-not-found failure, while release-only serving continues to work.

Written by the indexing model from the issue text.