[AI.a2ml] Add no-side-effect-imports directive for migration #50

Proposal

Add a (no-side-effect-imports) directive: AffineScript modules don't run code at load time. Migrating ReScript/JS code that uses let _ = X.foo for module-load side effects must be rewritten to call an explicit registration function.

Source observation

idaptik's src/Main.res has 22 let _ = X.constructor lines that exist only to trigger module-load side effects in JS-land. AffineScript compiles to wasm where there is no implicit module-load-time side effect to hook. The AffineScript translation in migration/main/Main.affine converts these to one explicit ScreenRegistry.registerAll(engine) call.

Suggested patch (LESSONS.md L6)

(directives
  (no-side-effect-imports
    (rule "AffineScript modules do not run code at load time. Migrating ReScript/JS code that uses \`let _ = X.foo\` for module-load side effects must be rewritten to call an explicit registration function.")))

Filed from idaptik Wave 3 pilot. See LESSONS.md and PILOT.md. Idaptik commit hyperpolymath/idaptik@aef38db.