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>

tests/ui/coverage-teardown.ts

@@ -5,9 +5,15 @@ import path from 'node:path';
 import { CoverageReport } from 'monocart-coverage-reports';
 import { coverageOptions } from './coverage.ts';
 
+/// Where a coverage run's page unit and native-bridge tests write V8's record of what they ran.
+export const NODE_COVERAGE = 'target/coverage/node-v8';
+
 export default async function teardown() {
   if (!process.env.IPX_COVERAGE) return;
-  const results = await new CoverageReport(coverageOptions).generate();
+  const report = new CoverageReport(coverageOptions);
+  // What the page's Node tests ran of it, when the run measured them first (NODE_V8_COVERAGE, #407).
+  if (fs.existsSync(NODE_COVERAGE)) await report.addFromDir(NODE_COVERAGE);
+  const results = await report.generate();
   if (!results) return;
   const lines = results.files.map((f) => ({ file: f.sourcePath, covered: f.summary.lines.covered, total: f.summary.lines.total }));
   fs.writeFileSync(path.join(coverageOptions.outputDir!, 'summary.json'), JSON.stringify({ lines }, null, 2));