test(browser): execute packed package in Chromium

[leoromanovsky]

Motivation

PR #344 adds production browser entry points and a React Native package smoke test, but the existing browser package check stops after TypeScript and Vite compilation. A package can build successfully while failing when its production output is loaded in a real browser, especially around package exports, initialization order, runtime globals, and capability-specific entry points.

This PR is stacked on #344 to close that runtime coverage gap before those browser APIs merge.

Changes

• add a Playwright Chromium smoke test to the isolated Vite test app
• build and serve separate pages for the full and /precomputed browser entry points from packed core/browser tarballs
• exercise protobuf configuration parsing, round-trip serialization, boolean and integer evaluation, and SHA-256 matching through the full entry point
• rerun the full entry point with TextEncoder, TextDecoder, and BigInt unavailable
• verify the precomputed entry point parses and round-trips precomputed data without retaining rules
• fail on browser page exceptions and console.error output
• update the package-install check to install only the Chromium headless shell, execute the smoke tests, and restore the root lockfile after temporary package wiring

Decisions

• keep this stacked on sameerank/FFL-2835/configuration-from-string because it directly tests the APIs introduced by [FFL-2835] Parse flags configuration wire format #344
• test packed artifacts through a production Vite build and preview server rather than workspace links or a DOM emulator
• keep the existing module-level assertion as the proof that /precomputed excludes Protobuf-ES; this browser smoke complements it by proving the entry point executes correctly
• install only Chromium's headless shell to limit CI download size while retaining the real browser runtime boundary

Validation

• yarn build
• yarn lint
• yarn format:check
• yarn test
• yarn test:browser-install (3 Playwright tests passed)

[Copilot]

Pull request overview

Adds real Chromium runtime smoke coverage for packed browser artifacts introduced by #344.

Changes:

• Builds full and precomputed Vite entry points.
• Tests parsing, evaluation, serialization, fallbacks, and browser errors.
• Installs Chromium and runs Playwright during package validation.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
test-app/vite.config.ts	Configures multi-page production builds.
test-app/tests/smoke.spec.ts	Adds Chromium smoke tests.
test-app/src/smoke.ts	Provides smoke assertions and result reporting.
test-app/src/precomputed.ts	Exercises the precomputed entry point.
test-app/src/main.ts	Exercises full configuration parsing and evaluation.
test-app/precomputed.html	Hosts the precomputed fixture.
test-app/playwright.config.ts	Configures Chromium and Vite preview.
test-app/package.json	Adds Playwright tooling and script.
test-app/index.html	Simplifies the full-entry fixture page.
scripts/test-package-install.sh	Runs browser tests against packed artifacts.

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[vjfridge]

The new coverage lgtm, thanks!

[sameerank]

Agreed with adding more test coverage 🙌