Build failure: `react-version` and `twoslash` suites fail with exit code 7/1

This issue was created by an agent analysing CI failures from the Next.js Deploy Suite (vinext main vs Next.js v16.2.6, 2026-05-22).

Problem

Several suites consistently fail the deploy script with Custom deploy script failed: undefined (7) (react-version) or (1) (twoslash), with no test ever running. The exit codes suggest a missing toolchain dependency or unsupported config (e.g. multi-package react resolution / TypeScript compile failure).

Custom deploy script failed: undefined (7) — react-version

Custom deploy script failed: undefined (1) — twoslash

Estimated Impact

~7 test failures across the deploy suite.

Affected Test Suites

• test/e2e/react-version/react-version.test.ts (5 failures)
• test/e2e/twoslash/index.test.ts (2 failures)

Recommendation

1. Reproduce first in vinext's own test suite. Run the deploy script directly against each fixture and capture the underlying stderr.

2. Triage the exit codes. Exit code 7 is commonly used by tools for unmet dependency / not found — confirm which dependency or stage emits it. Exit code 1 needs the captured error message to triage.

3. File targeted fixes. Both suites likely need separate root-cause fixes; this issue tracks the triage.

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Part of #1328.