fix(test): keep the suites off a developer's real database

bun loads a plain `.env` into process.env before anything runs, and
tests/helpers/env.ts read that as a deliberate export, so it beat `.env.test`
outright. `scripts/test.sh api` therefore pointed the api suites at whatever
deployment `.env` describes: `prisma db push --accept-data-loss` for the
schema, then a truncate of every table between tests. The e2e half was worse,
because playwright.config.ts built and started the app with that DATABASE_URL
and those R2 credentials, then wrote fixtures into it. CI never saw any of
this: a runner has no `.env`.

Three changes, in order of what each one catches:

- helpers/dev-env.ts drops the values bun copied out of a development env file,
  leaving `.env.test` to fill them. Only values that match the file
  character-for-character go, so a real export still wins and the per-suite
  databases of a parallel api run keep working.
- helpers/test-database.ts refuses a DATABASE_URL whose database name is not
  marked as a test one, at the single point every path into the setup passes
  through. This is the backstop, not the fix.
- playwright.config.ts blanks the variables a development env file defines and
  the config does not. Dropping them from process.env is not enough there:
  `next build` and `next start` run @next/env themselves and read the files
  again. That is also why a local e2e run could not build at all (a set
  DISABLE_RATE_LIMIT throws in lib/rate-limit.ts under NODE_ENV=production) and
  why auth.spec.ts failed on a machine with SMTP configured.

`scripts/test.sh` now creates `.env.test` from the committed example instead of
asking for a one-line copy, so the guard above is something nobody has to meet.

tests/helpers/env.ts

@@ -13,49 +13,18 @@
 // Contract: an already-exported variable always wins. `.env.test` fills the
 // gaps. That is what lets CI export DATABASE_URL for a service container
 // without needing a `.env.test` file at all.
+//
+// With one correction, see forgetAutoloadedDotenv in helpers/dev-env.ts: bun
+// populates process.env from a plain `.env` before any of this runs, which the
+// contract above would otherwise read as a deliberate export.
 
 import fs from 'node:fs';
-import path from 'node:path';
 import { config as loadDotenv } from 'dotenv';
 
-/**
- * Walks up from the working directory until it finds the checkout.
- *
- * This deliberately avoids `import.meta.url`, which would be the obvious way to
- * resolve a path relative to this file: Playwright transpiles TypeScript to
- * CommonJS unless package.json declares `"type": "module"`, and in CommonJS
- * `import.meta` is a *syntax* error, so the e2e suite could not import this
- * module at all. `__dirname` has the mirror-image problem under Vitest's ESM.
- *
- * The marker is prisma/schema.prisma as well as package.json, so a stray
- * package.json inside node_modules cannot be mistaken for the checkout.
- */
-function findRepoRoot(): string {
-  let current = path.resolve(process.cwd());
+import { forgetAutoloadedDotenv, REPO_ROOT, TEST_ENV_PATH } from './dev-env';
+import { assertTestDatabase } from './test-database';
 
-  for (;;) {
-    if (
-      fs.existsSync(path.join(current, 'package.json')) &&
-      fs.existsSync(path.join(current, 'prisma', 'schema.prisma'))
-    ) {
-      return current;
-    }
-
-    const parent = path.dirname(current);
-    if (parent === current) {
-      throw new Error(
-        `Could not locate the OpenFrame checkout from ${process.cwd()}: no ancestor ` +
-          'directory holds both package.json and prisma/schema.prisma. Run the test ' +
-          'suites from the repository root.'
-      );
-    }
-    current = parent;
-  }
-}
-
-export const REPO_ROOT = findRepoRoot();
-
-export const TEST_ENV_PATH = path.join(REPO_ROOT, '.env.test');
+export { REPO_ROOT, TEST_ENV_PATH };
 
 let loaded = false;
 
@@ -63,6 +32,8 @@ export function loadTestEnv(): void {
   if (loaded) return;
   loaded = true;
 
+  forgetAutoloadedDotenv();
+
   if (fs.existsSync(TEST_ENV_PATH)) {
     loadDotenv({ path: TEST_ENV_PATH, quiet: true });
   }
@@ -75,6 +46,10 @@ export function loadTestEnv(): void {
     );
   }
 
+  // Deliberately after the file load and before anything opens a pool: this is
+  // the one place every path into the test setup goes through.
+  assertTestDatabase(process.env.DATABASE_URL);
+
   // Vitest sets this already, but db-global.ts also spawns the Prisma CLI and
   // lib/rate-limit.ts throws when DISABLE_RATE_LIMIT is set in production.
   // @types/node declares NODE_ENV as read-only, hence the cast.