Fix meta shortcode truncating multi-word values in raw HTML contexts

[cderv]

When {{< meta key >}} appears in raw HTML contexts (include-after-body text blocks, raw HTML blocks), multi-word values are truncated to the first word. "Release Candidate" becomes "Release".

Root Cause

Shortcodes in raw text (RawBlock, CodeBlock, include text) are resolved by an lpeg parser that calls the handler with context = "text" and then stringifies the result (customnodes/shortcodes.lua:247-248). The text branch added by #14073 checked #optionValue > 0 to handle single pandoc-native Str nodes, but this matched any non-empty Inlines list. For [Str("Release"), Space, Str("Candidate")], only optionValue[1].text was returned.

Fix

Narrow the guard to #optionValue == 1 (exact single-Str match) and add an Inlines branch using pandoc.utils.stringify() which concatenates all inline elements. The Blocks path (pandoc.write(markdown)) is unchanged, preserving #14061 line-break behavior.

Fixes #14159

[posit-snyk-bot]

✅ Snyk checks have passed. No issues have been found so far.

Status	Scanner	Critical	High	Medium	Low	Total (0)
✅	Open Source Security	0	0	0	0	0 issues
✅	Licenses	0	0	0	0	0 issues

💻 Catch issues earlier using the plugins for VS Code, JetBrains IDEs, Visual Studio, and Eclipse.

[cscheid]

The service we use to get placeholder images seems to be failing. Another thing to replace with our own...