chore: modernize issue templates

[eitsupi]

Summary

• replace the legacy Markdown bug template with a structured Issue Form for reproducible bugs
• direct questions and troubleshooting to Q&A Discussions and feature ideas to Ideas Discussions
• hide blank issues from users with Read or Triage access and remove the feature request Issue template
• update the README to match the new reporting workflow

The form currently keeps environment details as separate structured fields so they can be validated and scanned during triage. These can be consolidated if the review finds the form too burdensome.

Maintainer workflow

Setting blank_issues_enabled: false does not prevent maintainers from opening blank issues. GitHub still shows a Blank issue — Maintainers only option to users with Write, Maintain, or Admin access, so maintainers can continue creating internal tasks and personal TODO issues. Users with Read or Triage access only see the configured templates and Discussion links. See the GitHub documentation.

Closes #1783

[ThomasSoeiro]

Maybe we should ask for sessionInfo() so we have languageserver et all. version, locale, OS...

[eitsupi]

Maybe we should ask for sessionInfo() so we have languageserver et all. version, locale, OS...

I considered it too, but I decided it was too risky because confidential information might be included.