Every /readers load logged a CSP violation: foliate-js injects its
reader-generated stylesheets as blob: URLs, and style-src only allowed
'self' 'unsafe-inline' — so the sheet was refused and selection/
highlight styling inside the reader rode on nothing.
blob: was already granted for img-src, font-src, and frame-src for
exactly this reader content; style-src now matches. The content is
app-generated at runtime (no cross-origin input), script-src is
untouched, and the strict script hash allow-list keeps its guarantee.
Pinned by TestThemeFlashGuardHashMatchesCSP (script-src only — the
style-src addition doesn't interact) and TestGoSourcesAreCSPSafe.