resolveDocLink doesn't handle extensionless links

[alsiola]

Bug

Internal links in MDX/MD files that omit the file extension (e.g. [Members](members) instead of [Members](members.mdx)) are not resolved as hash routes. They fall through as plain relative URLs, resulting in broken links (404s).

Root cause

resolveDocLink in src/app/src/lib/doc-links.ts requires the .md/.mdx extension to match:

if (!href.match(/\.mdx?(#.*)?$/i)) return null;

Extensionless hrefs return null, so the link is rendered as a plain <a href="members"> which resolves against the page's base URL instead of becoming #/doc/docs/admin/members.

Reproduction

Doxla's own docs have the same issue — docs/configuration.mdx links to (custom-components) and docs/custom-components.mdx links to (configuration), both without extensions. These links are broken on the live site.

The README.md link [Why Doxla?](RATIONALE.md) works because it includes the .md extension.

Expected behaviour

Extensionless relative links should be resolved against the manifest to check if they match a known doc slug, and rewritten as hash routes if so.

Workaround

Include the .md/.mdx extension explicitly in all internal links.