* Fix ASCII diagram rendering: use system mono font for box-drawing chars
Geist Mono renders box-drawing characters (┌─┐│└┘) at double width,
breaking alignment in the concepts page diagram. Use system monospace
fonts (Menlo, Monaco, Consolas) for ascii-variant code blocks, which
handle these characters at correct single width.
* Fix CSS specificity: code element was overriding pre font-family
.docs-content code sets font-family to Geist Mono, which overrides
the system mono font set on the parent pre element. Geist Mono is
loaded with Latin subset only, lacking box-drawing glyphs (U+2500-257F),
so browsers fall back to CJK-aware fonts that render them double-width.
Fix: add font-family: inherit to .docs-content pre code so code
elements inside pre blocks inherit the correct font from their parent.
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