[eas-cli] Validate legacy command/path local functions referenced from workflows

[sswrk]

Why

eas workflow:validate and eas workflow:create check referenced local functions before anything is submitted, so mistakes surface on the developer's machine instead of failing the build later. Completes the stack that lets custom build functions from .eas/build configs move into .eas/functions (#4095, #4096, #4097).

How

Validates function.yml files with the widened LocalFunctionConfigZ, so both shapes are accepted and a file mixing them is rejected with a readable error. For a path function, checks that the module directory and its package.json exist locally, resolving the path with the same shared helper the build runner uses and naming both the literal path: value and the resolved location in the error.

Test Plan

cd packages/eas-cli && yarn test src/commandUtils/workflow/__tests__/compositeFunctions-test.ts

Validation tests: a command function and a path function with an existing module pass; a missing module directory, a module without package.json and a config mixing both shapes each fail with a readable error.

Also smoke-tested end to end against a scratch project: validateWorkflowLocalCompositeFunctionsAsync accepted workflows calling a command function and a path function, and rejected a path function whose module directory was missing.

[linear-code]

ENG-25402

[sswrk]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• [eas-cli] Validate legacy command/path local functions referenced from workflows #4098 👈 (View in Graphite)
• [build-tools] Load legacy command/path local functions and resolve module paths #4097
• [steps] Expand legacy command/path local functions to a single build step #4096
• [eas-build-job] Accept legacy command/path custom function shape in function.yml #4095
• [eas-cli] Validate local composite functions referenced from workflow hooks #4064
• [build-tools] Load composite function catalogs for hook steps #4063
• [steps] Support local composite functions in hook steps #4062
• [steps] Unify the default gating of steps with no if: across steps, composite scopes, and hooks #4061
• [eas-cli] Validate local composite functions in workflow files #3931
• [build-tools] Load local composite function catalog at build runtime #3930
• [steps][4/4] Resolve composite function outputs #4015
• [steps][3/4] Interpolate composite function inputs #4014
• [steps][2/4] Expand composite function references into build steps #3929 : 1 other dependent PR (#4013 )
• [steps][1/4] Add isCompositeFunctionPath and reject local composite functions in custom builds #3956
• [eas-build-job] Add local composite function schema #3928
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 62.34%. Comparing base (548b648) to head (e34b99c).

Additional details and impacted files

@@                                     Coverage Diff                                      @@
##           szymonswierk/eng-25402-build-tools-load-legacy-functions    #4098      +/-   ##
============================================================================================
+ Coverage                                                     62.33%   62.34%   +0.02%     
============================================================================================
  Files                                                           996      996              
  Lines                                                         44881    44894      +13     
  Branches                                                       9443     9446       +3     
============================================================================================
+ Hits                                                          27973    27986      +13     
  Misses                                                        15462    15462              
  Partials                                                       1446     1446              

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[github-actions]

✅ Thank you for adding the changelog entry!