Preserve tasks named __proto__ in auto and autoInject - #2129

auto currently reports a recursive dependency when a task named __proto__ has a dependency, even for a valid acyclic graph. A task with that name can also lose its own property in successful and partial-error results. autoInject drops the same task name while constructing the task map passed to auto.

For example, this graph is rejected before either task runs:

async.auto({
    start: callback => callback(null, 1),
    ['__proto__']: ['start', (results, callback) => callback(null, results.start + 1)]
}, callback);

The dependency counts and autoInject task map now use null-prototype objects, and __proto__ results are stored as own data properties. The public results object keeps its usual prototype and property attributes, including when a task fails.

Twelve regression tests cover independent task values, a dependent task and downstream consumer, partial-error results, the Promise API, and explicit or inferred dependency injection. All 715 Node tests and ESLint pass. A separate agent also checked ordinary and null-prototype task maps, real cycles, and cancellation.

Prepared by a Codex agent and independently reviewed by another agent.