[codex] fix issue label class binding

[Sean-Kenneth-Doherty]

Summary

• Fix the dynamic issue label class binding in IssueList.astro.
• Let rendered issue cards receive either good-first-issue or help-wanted so the existing modifier styles apply.

Why

The previous class attribute included the conditional expression inside a plain string, so Astro rendered the expression text literally in the built HTML instead of evaluating it.

Validation

• pnpm build
• Confirmed dist/index.html renders Issue-Label good-first-issue and no longer contains {issue.priority ...}
• git diff --check

[Sean-Kenneth-Doherty]

Fresh validation against the current PR head (0936f70):

• the PR is scoped to src/components/IssueList.astro and fixes the issue-label class binding
• source now uses a template literal class expression instead of rendering the literal {issue.priority ...} string
• GITHUB_TOKEN=$(gh auth token) pnpm build -> Astro build succeeded, 2 pages
• generated dist/index.html contains 9 issue labels, 0 unresolved template-expression class strings, and rendered classes like Issue-Label good-first-issue
• git diff --check origin/main...HEAD -> clean

I validated this in an isolated temporary git worktree so generated .astro/dist output did not touch the main checkout.