A ```mermaid fence rendered as a wall of `graph TD` source on both surfaces.
It now renders as an SVG in the hub file viewer and on public /s/<token>
markdown share pages.
Mermaid ships inside the binary (no CDN, so air-gapped self-hosters keep
working) and is imported lazily: a document with no fence downloads none of
it. A fence that doesn't parse — the common case for hand-written wiki
diagrams — keeps today's <pre><code> plus a small note, and one bad fence
never stops the good ones beside it. A blocked or offline chunk lands in the
same place.
The share page is the harder half: it is server-rendered Go HTML with no
JavaScript, and its `sandbox allow-scripts` CSP makes the origin opaque, so a
module script and every import() it makes arrive with `Origin: null`. The CSP
is unchanged and gains no allow-same-origin; instead the real-asset branch of
frontend() now sets Access-Control-Allow-Origin, which only ever touches files
that are already public and cookie-less. The script tag itself is injected
only when the rendered document actually contains a fence.
Also fixes an embed bug this change surfaced: `//go:embed static` silently
skips names beginning with `_`, and Vite's first shared chunk is
`_commonjsHelpers-<hash>.js`. The build passed, the commit looked right, and
the served app was blank. It is `all:static` now, with a test that every file
on disk is in the binary.
