[steps][build-tools][eas-cli] Expand legacy command/path local functions to a single build step; rename references in the consumers

[sswrk]

Why

We want to grandfather the legacy reusable functions from custom builds (https://docs.expo.dev/custom-builds/functions/) into the new reusable functions that can be used in workflows. This is to make the migration from custom builds to workflows easier.

This PR adds support for parsing the legacy custom build functions into workflow steps.

How

First, across steps, and the consumers (build-tools and eas-cli):

• Rename “composite local function” occurrences to “local function” in places where we support both composite and legacy functions (this is done in the first commit so I recommend taking a look and then reviewing the rest of the commits to avoid the renaming noise).

The actual feature in steps:

• Load legacy functions in the local function catalog (utils/localFunctions.ts).
  • Functions that specify path: have the path resolved in this step.
• Map a legacy config to BuildFunction (utils/legacyFunction.ts).
  • Inputs and outputs default to required, which match the legacy functions, but is different from composites.
• Expand a legacy call into a single build step (LocalFunctionExpander). BuildStep already has the machinery to run such function.
  • Note: unlike composite functions, working_directory set by the caller is allowed, because there's just one step.

This affects consumers:

• build-tools: legacy functions referenced in workflows, hooks or composite functions used in workflows are now loaded.
• eas-cli: eas workflow:validate accepts legacy functions.

Test Plan

Added unit tests.

[linear-code]

ENG-25402

[codecov]

Codecov Report

❌ Patch coverage is 97.84946% with 4 lines in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (szymonswierk/eng-25402-eas-build-job-legacy-function-shape@124aed7). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
...es/eas-cli/src/commandUtils/workflow/validation.ts	33.34%	2 Missing ⚠️
packages/steps/src/index.ts	0.00%	1 Missing ⚠️
packages/steps/src/utils/localFunctions.ts	98.95%	0 Missing and 1 partial ⚠️

Additional details and impacted files

@@                                      Coverage Diff                                      @@
##             szymonswierk/eng-25402-eas-build-job-legacy-function-shape    #4096   +/-   ##
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  Files                                                                 ?     1011           
  Lines                                                                 ?    45832           
  Branches                                                              ?     9645           
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  Hits                                                                  ?    28651           
  Misses                                                                ?    15720           
  Partials                                                              ?     1461           

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[github-actions]

🤖 AI code review

Decision: No review — every pass failed

⚠️ The AI review could not complete: every review pass failed or timed out, so these changes were effectively NOT reviewed. Treat this as "no review", not "looks good".

⏱️ Coverage note: coverage is partial — some review passes did not
finish (timed out or failed), so issues may exist in areas not fully reviewed:

• The cross-file review (issues spanning multiple changed files) failed to run; those changes were not reviewed.
• The consistency review (part 2 of 3) failed to run; those changes were not reviewed.
• The consistency review (part 1 of 3) failed to run; those changes were not reviewed.
• The correctness review (part 1 of 3) failed to run; those changes were not reviewed.
• The consistency review (part 3 of 3) failed to run; those changes were not reviewed.
• The correctness review (part 2 of 3) failed to run; those changes were not reviewed.
• The correctness review (part 3 of 3) failed to run; those changes were not reviewed.
• The security review (part 1 of 3) failed to run; those changes were not reviewed.
• The security review (part 2 of 3) failed to run; those changes were not reviewed.
• The security review (part 3 of 3) failed to run; those changes were not reviewed.

No findings.

---

This review is advisory — it never blocks a merge and never auto-approves.

[sswrk]

Re. AI review:

Local function load errors use plain Error, not BuildConfigError

Not something specific to this PR, ignoring

[github-actions]

Subscribed to pull request

File Patterns	Mentions
packages/eas-cli/**	@douglowder

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[github-actions]

✅ Thank you for adding the changelog entry!