Convert bug report template to issue form

[coyaSONG]

Summary

• replace the Markdown bug report template with a structured GitHub issue form
• preserve the known #938 package-installation guidance and diagnostic/redaction instructions
• require duplicate checks, reproduction steps, actual and expected behavior, installation method, and version/environment details

Validation

• parsed the form with Ruby's safe YAML loader
• verified the required top-level keys, supported field types, unique valid IDs, and required inputs against GitHub's current issue-form schema
• ran git diff --check

No changelog entry is included because this changes the issue-reporting template rather than bat behavior.

Closes #1946.

Disclosure

This contribution was prepared with Codex and has not received human review before submission.

[coyaSONG]

I am limiting my concurrent review load in this repository to two PRs, so I am closing this older draft for now rather than leaving a third item in the maintainer queue. The linked issue remains open, the branch is current with master, and the existing CI evidence is preserved. This can be reopened after one of the two active slots clears.