tooling: convert issue templates to YAML issue forms (enforce required fields)

[JohnnyWilson16]

Problem

The issue templates (bug_report.md, feature_request.md, documentation.md) are classic Markdown, so required fields (repro script, versions, affected page) can't be enforced — reporters can submit without them.

Expected outcome

Equivalent GitHub issue forms (.yml) with the key fields marked required: for bugs, the minimal repro script + fd.profile(df) output + environment; for docs, the page/file link.

Relevant files

• .github/ISSUE_TEMPLATE/*.yml (replacing the .md variants)
• keep .github/ISSUE_TEMPLATE/config.yml (the Discussions/security contact links)

Acceptance criteria

• Forms render on GitHub's "New issue" chooser.
• Required fields block submission when empty.
• The existing config.yml contact links still appear.

Difficulty / skills

🏗️ mid — GitHub issue-form YAML schema. No code.