[baseballyama]

Why

The PNG path (@office-kit/pptx-preview/node) maps every authored font name through substituteFamily. A caller that measures a deck's font with its own face — e.g. a buildFontkitMeasurer alias from the template's font (Meiryo) to a face in fontFiles — gets lines wrapped for that face but painted in Carlito, so measured and drawn line breaks disagree. renderSlideSvg already takes resolveFamily; rasterize didn't forward it.

What

• RenderImageOptions.resolveFamily?: RenderSlideOptions['resolveFamily'] (same type as the SVG option, optional like the other fields), forwarded to renderSlideSvg.
• Order with eastAsianFamily (fix(preview): draw bold Japanese text with the bold face in PNG renders #481): East Asian characters take eastAsianFamily (the first kana face in fontFiles); the rest of the run takes the resolveFamily result. Fixed by a test.
• Unset → identical output (tested byte-for-byte against passing substituteFamily), so the fidelity baseline should not move.
• README section + minor changeset.

Tests

test/preview-raster-resolve-family.test.ts

• a Meiryo run resolved to a loaded family draws a wider ink bbox (and a different ink count) than the Carlito default; uses bundled Liberation Mono as the stand-in so CI needs no extra font
• the measurer receives the resolved family
• unset equals substituteFamily, byte-identical PNG
• with both options, CJK pieces are in eastAsianFamily and Latin pieces in the resolved family (SVG + measurer)

Both raster tests fail when the forwarding line is removed.

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