docs(github): update issue templates and triage workflow

[aheritier]

Modernize the GitHub issue templates for bugs and feature requests,
replacing informal formatting with structured Markdown sections.
Update the auto-triage workflow and nightly scanner to use GitHub's
native issue type system instead of kind/* labels.

Key changes:

• Rewrite bug report template with clearer sections for expected
  vs actual behavior, environment details, and error output
• Rewrite feature request template with motivation, use cases,
  proposed solution, and alternatives sections
• Add type: Bug and type: Enhancement frontmatter to use
  GitHub's native issue type system
• Remove kind/bug and kind/documentation labels from both
  templates and the nightly scanner, as issue type is now set
  via GitHub's native type field
• Update auto-triage workflow condition from checking for the
  kind/bug label to checking for issues with type Bug

[docker-agent]

Assessment: 🔴 CRITICAL

The auto-triage workflow condition uses github.event.issue.type which is not a valid GitHub Actions context field for the issues: labeled event — the triage job will never execute. Additionally, the nightly scanner's updated instructions claim issue type is handled natively but the gh issue create command lacks the required --type flag.

[docker-agent]

[HIGH] Triage workflow condition uses invalid github.event.issue.type field — job will never run

The workflow trigger is issues: types: [labeled], and the old condition correctly used github.event.label.name == 'kind/bug' (the label from the event payload). The new condition:

if: github.event.issue.node_id != '' && github.event.issue.type == 'Bug'

github.event.issue.type is not a valid field in the GitHub Actions issues event payload. GitHub's native "issue type" feature is not exposed in the webhook payload as github.event.issue.type — the issue object mirrors the GitHub REST API, which does not include a type field in the labeled event context. This means:

1. github.event.issue.type == 'Bug' will always evaluate as falsy
2. The entire triage job will never execute for any issue

Suggested fix: Either keep label-based triggering (add back a kind/bug-equivalent label and check github.event.label.name) or change the workflow trigger from types: [labeled] to types: [opened, edited, typed] — GitHub supports typed as an issue event type for native type changes — and query the issue type via the REST API in a step.

[docker-agent]

[MEDIUM] Nightly scanner instructions say issue type is set separately, but gh issue create lacks --type flag

The updated instructions state:

"Issue type is set separately via GitHub's native type system, not labels"

However, the gh issue create command shown in this diff does not include --type:

cat << 'EOF' | gh issue create \
  --title "$ISSUE_TITLE" \
  --label "automated" \
  --body-file -

The gh CLI supports --type <type> for issue type assignment. Without it, issues created by the nightly scanner will have no native type set, making them invisible to any type-based triage automation (including the updated auto-triage workflow). The instruction is misleading because it implies the type will be handled, but the actual command doesn't do it.

Suggested fix: Add --type "Bug" (for security/bug categories) to the gh issue create command, for example:

gh issue create \
  --title "$ISSUE_TITLE" \
  --label "automated" \
  --type "Bug" \
  --body-file -