Adds three standalone workflows that scaffold + convert an iOS app to
SwiftPM using the prebuilt XCFrameworks and compile it:

  - test-ios-spm-rntester.yml   (packages/rn-tester)
  - test-ios-spm-helloworld.yml (private/helloworld)
  - test-ios-spm-newapp.yml     (fresh copy of helloworld, wired to a
                                 Verdaccio-published local monorepo build)

None of these use @react-native-community/cli. Each workflow builds the
prebuilt dependencies + core XCFrameworks via the existing reusable
prebuild-ios-* workflows, primes both flavor slots, then runs the shared
logic in two committed, locally-runnable scripts:

  - scripts/e2e/spm-prime-artifacts.js  (lay CI tarballs + hermes into the
                                         --artifacts <dir>/<flavor>/ layout)
  - scripts/e2e/spm-ios-e2e.js          (scaffold -> spm add --deintegrate
                                         -> xcodebuild, per app)

Triggered manually (workflow_dispatch) and nightly (schedule).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

- spm-ios-e2e.js: build the execFileSync `env` from process.env's string
  entries only (process.env is Flow-typed to allow numbers, which the
  execFileSync `env` option rejects), and omit `env` entirely when there
  is no override so the child inherits process.env as-is.
- Both scripts: suppress the parseArgs [incompatible-type] error with the
  standard "Natural Inference rollout" $FlowFixMe, matching set-version.js
  and init-project-e2e.js.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Addresses review feedback that the original approach did not follow the
patterns already used in CI:

- The three workflows no longer trigger prebuild-ios-dependencies /
  prebuild-ios-core themselves. They are workflow_call-only and consume
  the ReactCore / ReactNativeDependencies artifacts produced elsewhere in
  the run, the way e2e-ios-templateapp does. The `slices` input added to
  the two prebuild workflows is reverted.
- They are invoked from test-all.yml instead of carrying their own cron.
  Note this means they run per-PR (gated on should_test_ios) and on
  pushes to main, not nightly -- test-all.yml has no schedule trigger.
  They start as continue-on-error so a brand-new lane cannot hard-block
  unrelated iOS PRs; remove that once it has proven green on main.
- The new-app workflow reuses the react-native-package artifact instead
  of rebuilding the npm package.
- Both helper scripts are deleted. Priming the artifact slots needs no
  new code: download-spm-artifacts.js already accepts tarball overrides
  via RN_CORE_TARBALL_PATH / RN_DEPS_TARBALL_PATH, so the workflows call
  `npx react-native spm download` directly, and the new-app case reuses
  scripts/e2e/init-project-e2e.js --useHelloWorld.

Debug and Release run as parallel matrix cells. Each cell stages both
flavor slots because `spm add` validates both (it stages both framework
trees and selects one via a per-configuration build setting).

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

react-native-xcode.sh already handles this: when there is no Pods
installation and the Pods hermesc path does not exist, it resolves the
hermes-compiler package through react-native's own dependency graph
(scripts/react-native-xcode.sh:83-99). Exporting HERMES_CLI_PATH from
the workflow bypassed that shipped resolution, so the Release cells were
not exercising what a real SwiftPM consumer does — and a harness-side
export of this variable has previously masked hermes VM/compiler
bytecode skew.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

All six cells (rn-tester, HelloWorld and a fresh app, Debug and Release)
passed in run 30379384838, so the lanes no longer need to be advisory.
Dropping continue-on-error means a SwiftPM regression fails test-all
instead of being reported as a green run with red cells inside it.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>