Adds .env support

[arcanis]

Add support for autoloading .env files as per the rules in Berry.

---

Note

Medium Risk
Introduces new startup-time behavior that reads .env files, mutates the process environment, and injects variables into all spawned subprocesses, which can affect runtime behavior and error modes if files are missing or malformed.

Overview
Adds support for auto-loading and injecting environment variables from project .env files (defaulting to optional .env.yarn?) into any subprocess spawned by Yarn.

Configuration loading is refactored into a multi-phase flow: pre-read rc files, minimally parse injectEnvironmentFiles, load/parse env files (with new error cases), temporarily set variables in the process environment to enable ${VAR} interpolation during config deserialization, and store the loaded env map on Configuration for later injection.

Updates schema to include injectEnvironmentFiles (and initScope), adds the dotenvy dependency, injects config.env_files into ScriptEnvironment::with_project, and tweaks the dotenv acceptance test to quote an interpolated value.

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[github-actions]

⏱️ Benchmark Results

gatsby install-full-cold

Metric	Base	Head	Difference
Mean	2.441s	2.443s	+0.09% ⚠️
Median	2.444s	2.441s	-0.10% ✅
Min	2.371s	2.377s
Max	2.498s	2.513s
Std Dev	0.028s	0.034s

📊 Raw benchmark data (gatsby install-full-cold)

Base times: 2.429s, 2.411s, 2.425s, 2.449s, 2.461s, 2.460s, 2.417s, 2.440s, 2.435s, 2.485s, 2.495s, 2.457s, 2.424s, 2.477s, 2.419s, 2.412s, 2.371s, 2.429s, 2.498s, 2.413s, 2.466s, 2.448s, 2.444s, 2.445s, 2.443s, 2.447s, 2.450s, 2.457s, 2.389s, 2.444s

Head times: 2.496s, 2.427s, 2.443s, 2.433s, 2.426s, 2.427s, 2.377s, 2.441s, 2.451s, 2.513s, 2.472s, 2.404s, 2.491s, 2.431s, 2.431s, 2.409s, 2.433s, 2.396s, 2.412s, 2.451s, 2.462s, 2.460s, 2.441s, 2.479s, 2.406s, 2.442s, 2.461s, 2.399s, 2.504s, 2.484s

---

gatsby install-cache-and-lock (warm, with lockfile)

Metric	Base	Head	Difference
Mean	0.359s	0.366s	+2.07% ⚠️
Median	0.357s	0.367s	+2.87% ⚠️
Min	0.349s	0.356s
Max	0.399s	0.375s
Std Dev	0.010s	0.005s

📊 Raw benchmark data (gatsby install-cache-and-lock (warm, with lockfile))

Base times: 0.370s, 0.359s, 0.368s, 0.354s, 0.358s, 0.364s, 0.362s, 0.371s, 0.371s, 0.357s, 0.351s, 0.351s, 0.356s, 0.356s, 0.359s, 0.360s, 0.399s, 0.350s, 0.350s, 0.351s, 0.357s, 0.352s, 0.359s, 0.351s, 0.354s, 0.351s, 0.357s, 0.354s, 0.357s, 0.349s

Head times: 0.366s, 0.372s, 0.367s, 0.359s, 0.357s, 0.364s, 0.361s, 0.367s, 0.365s, 0.363s, 0.367s, 0.356s, 0.367s, 0.375s, 0.368s, 0.361s, 0.367s, 0.364s, 0.373s, 0.364s, 0.371s, 0.369s, 0.369s, 0.362s, 0.364s, 0.368s, 0.364s, 0.369s, 0.369s, 0.375s

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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^{Reviewed by Cursor Bugbot for commit 0aa5b47. Configure here.}