[papers] regenerate all 13 dossier covers in vignette style

OpenAI billing raised; ran node papers/bin/gen-cover.mjs --all --force.
All 13 dossiers now have the canonical colored-pencil vignette covers
generated from their sourced cover-prompt.txt:

rhizome — tangled rhizome runners with CRT glyph
sfpc — book-as-circuit-and-handwriting with breadboard
eyebeam — circuit-iris eye
recurse — laptop with Mandelbrot recursion spiral
internet-archive — floating Greek Revival temple
mellon — brass balance scales with grant-letters
pioneer-works — arched window with Yellin glass-shards
new-inc — translucent hexagonal incubator pod
studio-museum — easel-and-stool with Adjaye facade
hathitrust — book stack with data-strands
the-kitchen — Sony Portapak with cable braid
machine-project — Echo Park storefront window
heavy-manners-library — dub-reggae sleeve with library checkout pocket

Each cover replaces either an old vertical-strip or a cream placeholder.
Sources documented in each dossier's figures/cover-sources.md.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>