Add a terminal skin, and make the board's branding settings real

[ralyodio]

board.accent, board.logoUrl, board.faviconUrl and board.theme have been in DEFAULT_SETTINGS since the beginning and were read by nothing — a board could set an accent and watch the page not change. All four work now, and there is a third skin to use them with.

The terminal skin

A layer over the modern sheet, exactly as classic is, so a component's structure stays defined in one place:

• neutral surfaces, so the accent is the only colour on the page
• hairline rules instead of shadows — depth the way a tiling terminal separates panes
• monospace for chrome (nav, meta, counts, buttons), proportional for prose, because reading a paragraph in a monospace face is the part of the aesthetic that actually hurts
• the three dots of a title bar on section headers, drawn as one element's box-shadow so no markup changes and nothing reaches the accessibility tree

Nothing in it hard-codes a hue. It is a green board, an amber one or a blue one depending on board.accent.

The accent is derived, not stored twice

A colour legible on a dark board is usually illegible on a light one — #5fff87 reads beautifully on near-black and vanishes on white. So the chosen hue is emitted darkened for the light theme and brightened for the dark one, and every token that follows the accent (--ring, --primary-hot, --gradient-brand, --glow-primary, --page-wash, --row-hover) moves with it. One setting, readable in both themes.

It is baked into the stylesheet rather than written as an inline <style>: style-src carries no 'unsafe-inline', and widening the policy for a handful of custom properties is a poor trade. Because the sheet is served under a content hash, changing the accent in the admin panel changes the URL, so the new colour reaches a returning reader immediately instead of waiting out a year-long max-age.

board.accent defaulted to #4f46e5, an indigo nothing read. Wiring that up as-is would have repainted every existing board on upgrade, so the default is now empty — meaning "the built-in palette".

Two bugs found on the way

• The footer's GitHub link was broken by the board's own CSP. It carried style="display:inline-flex;…", and style-src governs style attributes, not only <style> blocks — so the icon sat above the word instead of beside it. It is a class now. 30 more inline style attributes elsewhere in the app are refused the same way; that is a separate change, not this one.
• /prefs/theme deleted the cookie for "system" instead of storing it. Identical behaviour on a board that defaults to system, and wrong on any other: a dark-default board would read the absence of a cookie straight back as dark, so the three-state toggle cycled dark → dark. All three choices are stored now.

Checks

pnpm typecheck clean, pnpm test 156/156 (10 new: the colour maths, the skin layering, the accent in the served sheet, logo/favicon in the header, and board.theme never overriding a reader's cookie).

Not run: pnpm format. It reformats ~70 files at HEAD and breaks two tests, so this branch is hand-formatted to match the surrounding code.

Rendered at 1280px, dark and light, with the HQTUI wordmark and #5fff87.

🤖 Generated with Claude Code

https://claude.ai/code/session_01JQRBzkLAusnFQHWMjgBLDZ