eqosys menus: a game injects its skin once and every shared surface wears it, hill climb to 8/10, rounds 5+ (from #3570) #3600

Score: 6.5/10 (target 8), after round 4 (PR #3597; the hook merged in #3540; earlier rounds 7, 7.5 and 7, each from a fresh judge). Moved up from #3570: its round 4 comment has the shots and the Next list. Per-game skins are #3598.

The owner's brief (2026-11-04): every game should be able to inject its own style into the eqosys menus. Today the shared sign-in client (packages/util/src/eqosys.ts) renders nothing, but the pieces games mount from it do, each in its own way: the report button (packages/util/src/report.ts) carries hard-coded inline cssText (grey border, white background, system font) that looks the same in a space-marine war room and a druid's tome; the spaces panel (spaces.ts) and lobby (lobby.ts) leave skinning to the page, so each game has its own account box (apps/*/src/account.ts, Two Fronts's account box in main.ts). The house kit (packages/ui) already re-themes by CSS custom properties (applyTheme, TOKENS), and packages/game-controls/src/skins.ts has classic / house skins with installStyles.

Goalpost

One way for a game to say "here is my skin" once, and every eqosys-rendered surface in that game wears it: sign-in / account chip, achievement toast, report button and form, party and spaces panels, lobby. Scored out of 10 by an agent judge against:

1. One injection point. eqosys({ app, url, from, prefix, skin }) (or a sibling skinEqosys(...)) takes a Theme of --ui-* tokens plus optional extra CSS, and every shared surface reads tokens from packages/ui instead of hard-coded colours. No per-surface styling API.
2. No hard-coded colours or fonts left in report.ts, spaces.ts, lobby.ts, and the achievement toast: every colour, radius, border and font is a --ui-* token with a house default.
3. Three games wear it. Two Fronts (distressed metal: --imperial fonts, brass on dark steel, square corners), Mythic Masters (tome: parchment, ink, Covered By Your Grace for the Book's hand; look at apps/mythic-masters/src/tome.css), Skate Tech Park (stay minimal: the house skin). Each injects its skin in its eqosys.ts and deletes any duplicate styling of those surfaces from its own CSS.
4. Cut before you add. The per-game account boxes that do the same thing (apps/*/src/account.ts) share one accountChip(...) in packages/util that the skin styles; copies die in the same PR.
5. One journey test per touched game still passes (eqosys.test.ts), plus one test that a skin's tokens land on the mounted surfaces (eval the computed style, don't assert on source text).

The loop

Each round is one PR against main that says "Part of #N". Score it with bun run probe <app> --shot on each game's sign-in chip, report form and achievement toast, side by side. End the round with a comment here starting Score: x/10 (target 8) and ending Next: ..., then open the "rounds N+" issue and close this one with "Moved up to #new".

Why first: the per-game artwork climbs (Two Fronts distressed metal, Mythic Masters tome) hang their menu skins on this hook.

Round 5 starts here

• A test that the eqosys badge's computed look is identical in all three skins.
• Mythic's settings-pane account row on accountChip (also in eqosys skin: each game injects or updates its skin through the merged hook (three lines per game) #3598).
• On a phone, a bottom-sheet report form that doesn't cover the menu, and a toast clear of the top bar.
• Real-game skin journeys for Mythic and Skate.