Make batch connect script files executable

[Guflly]

What does this PR do?

Makes the default batch-connect script executable before starting it. Custom run_script values and subclass overrides are left unchanged.

Related issue

Fixes #948

Testing

• Tests included
• bundle _2.7.2_ exec ruby -Itest -rminitest/autorun test/batch_connect/template_test.rb

Checklist

• Follows project code style and conventions
• No documentation changes needed; this does not change the public interface

[johrstrom]

Thanks, I've just got to pull this down and ensure it works.

[Bubballoo3]

Hey @Guflly, thanks for responding to the review feedback and for the thorough testing. You may have missed this but we recently published an AI policy on our main repository in OSC/ondemand#5646, and I wanted to get some info about your setup both for records and credit attribution, as well as to ensure that it is in line with our policy we established in that PR, which states

AI tools can be used to help with code, documentation, review, or other contributions, but a person must understand, review, answer questions, and take responsibility for anything they submit to this repository.
AI agents or bots may not submit contributions or interact with the community on someone’s behalf. Content submitted without meaningful human involvement will be rejected and closed. Additionally, accounts that repeatedly do this may be blocked or reported.

Before we continue reviewing this PR, would you mind answering the following questions?

1. To what extent was AI used in writing your change, and which model/format was used (eg. Opus 5 chatbot, GPT-5.6 agents)
2. Can you confirm that you personally (a human) understand these changes and can take responsibility for responding to questions or requested revisions
3. How did you come across this issue/repository? Is this something you have personally encountered as a user of the gem?
4. Did you test this change locally outside of the test suite? If so, how?