[eas-cli] Add lockfile existence preflight check for eas build

[AbbanMustafa]

Why

~3k builds fail weekly during install_dependencies because of lockfile issues. The most basic failure mode, a missing lockfile, can be caught before the build is even queued, giving instant feedback instead of waiting for a remote build to fail.

This is the first of several small PRs breaking up #3434

How

Added a single preflight check in prepareAndStartBuildAsync() that verifies at least one known lockfile (package-lock.json, yarn.lock, pnpm-lock.yaml, bun.lockb, bun.lock) exists in the project directory or workspace root (monorepo support via resolveWorkspaceRoot).

• The check runs once per CLI invocation using a module-level flag, matching the existing metroConfigValidated/sdkVersionChecked pattern.
• Skipped for local builds (localBuildMode), since local builds install deps locally.
• Opt-out via EAS_BUILD_SKIP_LOCKFILE_CHECK=1 env var.

Test Plan

Unit tests covering all lockfile types, missing lockfile error, and monorepo scenarios

Verified cli output

eas build
✔ Select platform › Android

⚠️ Detected that your app uses Expo Go for development, this is not recommended when building production apps.
Learn more
To suppress this warning, set EAS_BUILD_NO_EXPO_GO_WARNING=true.

Resolved "production" environment for the build. Learn more
Environment variables with visibility "Plain text" and "Sensitive" loaded from the "production" environment on EAS: EAS_USE_CACHE, EAS_VERBOSE, EXPERIMENTAL_EAS_GRADLE_CACHE.

✔ Incremented versionCode from 17 to 18.
No lockfile found in the project directory.
A lockfile is required to ensure deterministic dependency installation in EAS.
Run your package manager's install command (e.g. "npm install") to generate one.
To skip this check, run this command with EAS_BUILD_SKIP_LOCKFILE_CHECK=1.
    Error: build command failed.

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Subscribed to pull request

File Patterns	Mentions
**/*	@douglowder
packages/eas-cli/src/build/**	@sjchmiela

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⏩ The changelog entry check has been skipped since the "no changelog" label is present.

[codecov]

Codecov Report

❌ Patch coverage is 82.60870% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 55.88%. Comparing base (e74c93d) to head (20ec701).

Files with missing lines	Patch %	Lines
packages/eas-cli/src/build/runBuildAndSubmit.ts	33.34%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #3665      +/-   ##
==========================================
+ Coverage   55.87%   55.88%   +0.02%     
==========================================
  Files         868      869       +1     
  Lines       37545    37568      +23     
  Branches     7835     7841       +6     
==========================================
+ Hits        20973    20992      +19     
- Misses      16474    16478       +4     
  Partials       98       98              

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