docs: add CENTRAL.md as living orientation doc

Working notes for cross-session context: project shape, conventions,
in-flight work (FTW mode + light-mode rehaul), git protocol, recovery.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: 2 people

CENTRAL.md

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+# CENTRAL.md — Working notes and orientation
+
+Living doc kept by Claude across sessions. Update after each big change. If you're picking up cold: read this top-to-bottom, then `git log --oneline -20`, then dive in.
+
+## Project shape
+
+DBSMO is a Next.js 15 (App Router) Postgres+Prisma platform for self-paced math olympiad training at Diocesan Boys' School. Everything is server-rendered by default; a handful of `"use client"` components handle interactive UI (typewriter greeting, theme toggle, answer grid, FTW match).
+
+Stack: Next.js, NextAuth (Google + dev bypass), Prisma, KaTeX for math, Lucide icons, Vitest. No Tailwind — single 5k-line `app/globals.css`.
+
+## Where things live
+
+- `app/` — routes. Server components unless marked `"use client"`. Admin under `app/admin/*`.
+- `app/api/**/route.ts` — REST handlers.
+- `lib/` — shared logic: `auth.ts`, `db.ts` (Prisma singleton), `grading.ts`, `permissions.ts`, `visibility.ts`, `analytics.ts`, plus the `import/` ZIP+JSON pipeline.
+- `prisma/schema.prisma` — single source of truth for the data model.
+- `tests/` — Vitest specs for grading, tags, ordering, visibility, import.
+- `app/globals.css` — all styles. Light mode at the top (`:root`), dark via `@media` and `html.dark`.
+
+## Conventions
+
+- Page files do their own `getServerSession` + permission gate; no shared middleware.
+- Permission keys in `lib/permissions.ts` — `admin:view`, `admin:content`, etc. Use `hasPermission(role, key)`.
+- LaTeX statements rendered through `<LatexStatement>` (KaTeX auto-render).
+- Answer normalisation lives in `grading.ts`; do not roll your own comparison.
+- CSS variables drive theming. Add new colors as variables in `:root` AND in dark overrides — both. Don't hard-code hex outside `globals.css`.
+
+## What's currently in flight
+
+### Now (this session)
+
+- **FTW (Alcumus For The Win) mode** — speed-based timed problem race against the clock. Single-player first; friends-async leaderboard. Scoring rewards fast correct answers (AoPS-style: max points decay with elapsed time). Routes under `/ftw`, schema additions `FtwMatch`/`FtwAnswer`. Gets a sidebar entry.
+- **Light-mode rehaul** — current light theme reads as flat AI-generated. Goals: warmer paper-white background, deliberate ink colors, fewer purple/cyan washes, pink reserved as accent (matches dark). Keep dark+pink as-is.
+- **Less AI vibe** — copy passes (no eyebrow soup, no "hero panel" walls of cards), tighter spacing, fewer gradients. Keep the typewriter greeting unchanged.
+
+### Next (after the above lands)
+
+- `/simplify` pass on the codebase.
+- Sweep for dead code and CSS leaves now that several features have rotated through.
+
+## Testing locally
+
+```bash
+npm run typecheck   # tsc --noEmit
+npm run lint
+npm run test        # vitest
+npm run build       # next build (catches CSS/JSX issues at scale)
+npm run dev         # next dev — open http://localhost:3000
+```
+
+`npm run dev` may fail without `DATABASE_URL`. Pages that hit Prisma will 500; static routes still render. `next build` runs without DB.
+
+## Git protocol for this repo
+
+- Push checkpoints to `origin/main` after each big milestone (user has bypass perms enabled and asked for this).
+- Use HEREDOC commit messages, two short paragraphs max.
+- Never `--no-verify`, never amend pushed commits, never force-push.
+
+## Recovery
+
+If a file goes missing:
+```bash
+git fetch origin
+git checkout origin/main -- <path>
+```
+Then read the file, reconcile with what's in memory, keep going.
+
+## Open questions / followups
+
+- Realtime multiplayer FTW would need Pusher / WebSockets — out of scope for now. Async friend matches first.
+- `/api/practice/tags` is referenced from `practice/page.tsx` but I haven't reviewed it; check before touching.
+- `globals.css` has a "2026 refresh" overlay starting around line 2175 — overrides earlier rules. Edit there for visual changes, not the top.