[aversini]

Introduce platform targeting for bundle builds: add --platform/-p flag (auto|browser|node) with alias support and validation. Implement normalizePlatform and isValidPlatform helpers, wire platform through CLI parsing, bundlecheck, bundler and trend logic, and pass platform to esbuild. Auto-detect platform from package.json engines when platform is "auto"/undefined; treat packages with engines.node (and no engines.browser) as node. For node platform gzip sizes are not calculated (gzipSize becomes null) and UIs/tests updated accordingly. Update README and add/adjust tests to cover normalization, auto-detection, rendering (trend) behavior, and bundle checks.

[Copilot]

Pull request overview

This PR adds explicit platform targeting to bundlecheck, allowing builds for browser or Node.js and auto-detecting platform from package.json engines, and updates the CLI, core bundling logic, trend reporting, tests, and README accordingly.

Changes:

• Introduces normalizePlatform and isValidPlatform helpers, adds a --platform/-p CLI flag (with aliases and validation), and wires the normalized platform through to checkBundleSize, analyzeTrend, and esbuild.
• Enhances bundling behavior to auto-detect Node packages via engines.node (when engines.browser is absent), sets BundleResult.platform, and skips gzip computation for Node (gzipSize is now null there).
• Updates trend graph rendering and summaries to handle gzipSize: null, adds focused tests for platform normalization/detection and trend behavior, and documents the new flag and platform semantics in the README.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
packages/bundlecheck/src/defaults.ts	Adds defaultFlags.platform, and implements normalizePlatform/isValidPlatform helpers used to normalize and validate platform values.
packages/bundlecheck/src/parse.ts	Extends CLI parsing with a --platform/-p flag, usage examples, and a validation restriction that rejects invalid platform values.
packages/bundlecheck/src/bundler.ts	Extends bundle options/results with platform, reads engines from package.json, auto-detects browser vs node, passes platform to esbuild, and skips gzip for Node (returning gzipSize: null).
packages/bundlecheck/src/trend.ts	Threads the platform option through analyzeTrend, changes TrendResult.gzipSize to `number
packages/bundlecheck/src/bundlecheck.ts	Normalizes CLI --platform to canonical values, passes platform to bundle/trend functions, and updates the CLI output to show platform (with auto-detection note) and handle gzipSize: null for Node.
packages/bundlecheck/src/__tests__/defaults.test.ts	New tests verifying platform normalization (aliases, case/whitespace, auto) and validation rules for valid/invalid platform values.
packages/bundlecheck/src/__tests__/bundler.test.ts	Adds a dedicated platform option suite to assert default/explicit platform behavior, auto-detection from engines, gzip handling for Node vs browser, and that esbuild receives the correct platform.
packages/bundlecheck/src/__tests__/trend.test.ts	Extends trend tests to cover gzipSize: null handling in graphs and summaries, and to assert that the platform option is correctly passed to checkBundleSize.
packages/bundlecheck/README.md	Documents platform support, the new --platform flag, auto-detection behavior from engines, and the fact that gzip size is omitted for Node platform and shown as “N/A”.