fix(job): remove redundant shebang and set -e from BashTrial.build()

[BCeZn]

Problem

BashTrial.build() currently wraps the user script with boilerplate:

lines = ["#!/bin/bash", "set -e", ""]

Both are unnecessary:

• #!/bin/bash — the executor calls bash {script_path} directly, so the shebang is never interpreted
• set -e — silently injected behavior the user didn't ask for, can cause unexpected exits

Fix

Simplify build() to return the script as-is:

def build(self) -> str:
    return self._config.script or ""