web: pad the commit info card, render its message as AsciiDoc

The commit detail page’s subject/message/meta block had no padding at all, sitting flush against the surrounding card’s border. It also rendered the message body as a raw preformatted monospace blob instead of through the AsciiDoc pipeline every other free-text body (an issue, a .adoc file) already goes through, so a backtick-quoted command just showed as literal backticks in a wall of text instead of a code span.

.commit-msg now renders via crate::asciidoc::to_html (same plain-text fallback issue bodies use) inside .doc-body, scaled down to this compact context. Since .doc-body’s own code-span styling depends on <code>` reading as a chip by default, added that as this stylesheet’s base code rule and reset it back to plain inline text in .blob-code, the one context (per-line syntax-highlighted source) that needs <code> to carry no chip styling of its own.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>