[Mistium]

Stacked on #68. Merge MistWarp/docs#18 alongside it: the README now links to the Backend section that PR adds.

The API was 140 files at the repo root sharing one namespace: 1,418 functions and 463 globals, each file imported into main.osl in an order that mattered, and every route in one 600-line list. It's now organised by domain:

main.osl        imports the domains, runs startup and migrations, registers routes, starts the server (722 → ~170 lines)
src/
  config/ core/ http/ auth/ storage/ projects/ history/ git/
  games/ realtime/ community/ admin/ classroom/ rotur/

• Explicit public surfaces. Each file has an export {...} block listing what other directories use: 491 of 1,605 top-level names. The rest are private.
• Routes live with their domain. Each directory registers its own in routes.osl (registerProjectRoutes(api) and so on), and main.osl calls them in the same order as before.
• Caches sit next to the code that uses them, and tests beside the files they test.
• History is kept. Every file moved with git mv in a commit of its own, so git log --follow works.

Tooling

• opal.json holds the usual commands.
• CI (.github/workflows/test.yml) type-checks, tests, compiles and runs the smoke test on every PR, with OSL pinned to a commit and built from a clone.
• scripts/route_dump.py prints every route with its middleware.
• scripts/check_conventions.py rejects code comments and em dashes in added lines. A linter written in OSL will replace it in a follow-up.

Docs. The README is now an overview. Its 250 lines of reference material moved to the Backend section of the docs (MistWarp/docs#18). AGENTS.md tells coding agents the layout, the /v1 contract, the OSL 3.0 traps and the checks.

Behaviour is unchanged

• The route dump finds 634 routes, each with its middleware chain and method order, identical before and after.
• osl test passes 45/45.
• The smoke responses match between main (old compiler), Build on OSL 3.0 #68 and this branch.
• Startup order was compared from the generated Go: config now runs first, and every other file's top-level code only reads config, creates caches or defines constants.

An independent review confirmed it's a pure move and checked the startup order, the deploy layout (compiling from the repo root, build.sh, go.mod, native/, relative data/ paths) and CI. Its findings are addressed.

There is no visible change.