Coverage measures the page's Node tests and runs the Rust on Postgres (#407)

page-unit.ts and native-bridge.ts run the page's script outside a
browser, so the page's coverage counted none of what they test, and
native.ts read as mostly untested. In a coverage run they now run the
script from a file of its own, named as the browser names it, under
NODE_V8_COVERAGE (scripts/coverage-node.sh, before the browser suite in
npm run coverage:page and coverage.sh api), and the report's teardown
takes their record in, mapped to web/src by the build's source map: the
page's lines went from 73.3% to 80.0% of 3,043, native.ts to 93 of 120.

The cargo tests in coverage.sh's container run on Postgres, as
production does, when IPX_TEST_DATABASE_URL names the _test database,
from the shell or else /src/.envrc (that variable only); on SQLite
without it. The integration tests' own files are left out of the
totals; a crate's inline mod tests cannot be on stable Rust.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

package.json

@@ -7,7 +7,7 @@
   "scripts": {
     "build": "node web/build.mts",
     "typecheck": "tsc -p . --noEmit false --declaration --emitDeclarationOnly --outDir target/page-types && tsc -p tsconfig.sw.json && tsc -p tsconfig.tools.json && tsc -p tsconfig.k6.json",
-    "coverage:page": "IPX_COVERAGE=1 playwright test",
+    "coverage:page": "sh scripts/coverage-node.sh && IPX_COVERAGE=1 playwright test",
     "smoke": "node tests/page-smoke.ts",
     "test": "playwright test",
     "test:headed": "playwright test --headed",