[vicmaster]

canvas_evaluate's contrast check walked up from a text node to the nearest fill and used it as solid paint. It dropped the fill's alpha. A translucent fill was judged as its opaque color, so a common selected-state tint, rgba(245,158,11,0.08) over a near-black #14110c panel, was judged as solid amber. Light text on it was reported at 1.72:1 as a WCAG error; the real contrast is 13.45:1. A fully transparent fill, rgba(0,0,0,0), was read as solid black. Translucent text colors were treated as opaque too.

This showed up when the published viewer was imported and evaluated with framesmith itself: its selected breakpoint button got a false contrast error. App screens use tinted selected and hover fills on almost every list and toolbar, so the bug would misfire constantly on them.

The fix

• The check now collects fills from the text's parent upward until it reaches an opaque one. Translucent fills (rgba or #RRGGBBAA) are blended over what is behind them. When no opaque fill is behind them, they are blended over the white page, which is what the renderer shows.
• A translucent text color is blended into that background before the ratio is computed.
• transparent, none and zero-alpha fills are see-through; the walk continues past them.
• A fill the parser cannot read, such as hsl() or a named color, still stops the walk and skips the check, as before, so nothing is measured against the wrong background.
• When blending happened, the message names both the fill and the result, for example rgba(255, 255, 255, 0.1) (composited: #1a1a1a). The autofix color is picked against the blended background.

The fix cuts both ways. A faint white wash over black is now judged dark, so dark text on it fails, where it used to pass against "white".

The canvas_evaluate docstring and docs/GUIDELINES.md now say contrast is measured as rendered.

Testing

• New test-contrast-alpha.ts (fast tier, 10 checks): the viewer's tint, the same tint as #RRGGBBAA, a white wash over black, a fully transparent fill, translucent text, a tint with no opaque fill behind it, the transparent keyword, an unreadable hsl() fill, the composited color in the message, and an unchanged opaque pair. Seven of the checks failed on the old code.
• npm run test:fast: 82/82.
• npm run test:full: 119/119. Fifteen browser tests launch Puppeteer directly and need PUPPETEER_EXECUTABLE_PATH; they were run with it set.