fix: shadow global Symbol in async-iterator to resolve lint

[Planeshifter]

Failing run: https://github.com/stdlib-js/stdlib/actions/runs/25195861572 (issue #11867, 2026-05-01)

Symptom:

lib/node_modules/@stdlib/symbol/async-iterator/lib/main.js
  42:65  error  The 'Symbol.asyncIterator' is still an experimental feature and is not supported until Node.js 10.0.0. The configured version range is '>=0.12.18'  n/no-unsupported-features/es-builtins

Root cause:

eslint-plugin-n's no-unsupported-features/es-builtins rule flags any global Symbol.* property access when the package's engines.node range predates the Node.js version that introduced that property. The package declares >=0.12.18, but Symbol.asyncIterator requires Node ≥ 10. Because no local Symbol binding existed in the file, the rule saw the global and triggered.

Fix:

Add var Symbol = require( '@stdlib/symbol/ctor' ); to the // MODULES // section. A local binding named Symbol shadows the global; the rule no longer applies its version check to Symbol.asyncIterator. Runtime behavior is unchanged — hasAsyncIteratorSymbolSupport() already guards the ternary, so the Symbol.asyncIterator property is never evaluated in environments where the stdlib Symbol polyfill would return undefined. This is the identical pattern used in @stdlib/symbol/to-primitive (line 24 of its lib/main.js).

Validation:

• Confirmed the change mirrors @stdlib/symbol/to-primitive/lib/main.js exactly.
• @stdlib/symbol/async-iterator/package.json has empty dependencies: {}; this matches the established sibling pattern (to-primitive also has empty deps but requires @stdlib/symbol/ctor).
• Three independent reviewers (two opus, one sonnet) all approved in the first cycle:
  • Reviewer A (correctness): fix silences the lint rule; hasAsyncIteratorSymbolSupport() guard prevents any runtime error in environments where ctor returns undefined; only one Symbol.* reference in the file.
  • Reviewer B (regression): no consumer packages affected; shadowing is module-scoped; change is one line; no import cycle; package.json update not required.
  • Reviewer C (style): spacing and placement match stdlib conventions exactly; fix is an exact structural match to the sibling pattern.

Reviewer notes:

• Reviewer A noted that @stdlib/symbol/ctor returns void 0 (not null) on Symbol-unsupported environments; the brief's description said null. This is a documentation inaccuracy in the brief only — runtime behavior is correct because the guard prevents the property access.
• Reviewer C noted the commit subject is ~85 characters, slightly over the 72-character guideline. Retained for clarity; can be shortened at maintainer discretion.

Related: issue #11867 (cluster 2 of that issue — utils/constructor-name — is addressed in a separate draft PR)

Contributing Guidelines

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Generated by Claude Code

[stdlib-bot]

Coverage Report

Package	Statements	Branches	Functions	Lines
symbol/async-iterator	$\color{green}91/91$ $\color{green}+100.00%$	$\color{red}2/3$ $\color{green}+66.67%$	$\color{green}0/0$ $\color{green}+100.00%$	$\color{green}91/91$ $\color{green}+100.00%$

The above coverage report was generated for the changes in this PR.