nav-item: wire the `raw` argument through from the shortcode

[markdumay]

assets/nav-item.html already accepts a raw field that bypasses Page.RenderString for a tab-pane body, but layouts/_shortcodes/nav-item.html never passes it and no caller in the module sets it — so the field is unreachable from markdown.

That matters on any site running markup.goldmark.renderer.unsafe = false. A nav-item whose body is a single nested shortcode emitting raw HTML (a grid, a chart, a custom table) reaches RenderString as literal raw HTML, and CommonMark then comments out or garbles the block. The pane renders as escaped text instead of the component.

Suggested fix, matching the existing $parentFade pattern in the same file (so a real false is not clobbered by | default):

{{- $raw := false -}}
{{- if and .IsNamedParams (isset .Params "raw") }}{{ $raw = partial "utilities/CastBool.html" (.Get "raw") }}{{ end -}}

then pass "raw" (cond $raw $body "") in both partial "assets/nav-item.html" calls (the tab output and the accordion alternative). Opt-in and defaulting to false, so every existing call site is unaffected — "" is falsy in the or that selects the body.

Verified working against v3.16.3 as a local override on a downstream site, where it is carried as an explicit interim fork pending this change.

[markdumay]

Fixed by #2127 — adds an opt-in raw-body boolean to the shortcode that passes the already-resolved body through as the partial's existing raw field.

Implemented as a separate argument rather than exposing raw directly: raw carries resolved HTML, which cannot sensibly come from a shortcode attribute, whereas raw-body is the flag saying the body is already HTML. Defaults to false, so existing call sites are untouched.