Fix retry handler treating undefined/null/NaN/Infinity as retry signal

[YunchuWang]

The tryHandleRetry method used a negative check (retryResult !== false) to determine if a custom retry handler wanted to retry. This treated any non-false value — including undefined, null, NaN, and Infinity — as a retry signal, causing infinite retry loops or invalid timer creation.

Changed to a positive check that only accepts explicit true or finite numbers: retryResult === true || (typeof retryResult === 'number' && Number.isFinite(retryResult)).

Added 6 new unit tests covering: undefined return, null return, positive delay (number), zero delay, NaN, and Infinity.

Fixes #140

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[Copilot]

Pull request overview

This PR fixes a runtime bug in the core orchestration executor retry flow where a custom async retry handler returning any value other than strict false (e.g., undefined, null, NaN, Infinity) was incorrectly treated as a “retry” signal, potentially causing infinite retries or invalid retry timers.

Changes:

• Update tryHandleRetry to retry only when the handler returns true or a finite number.
• Add unit tests validating no-retry behavior for undefined/null/NaN/Infinity and correct behavior for finite numeric delays (including 0).

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
packages/durabletask-js/src/worker/orchestration-executor.ts	Tightens retry-handler result validation to prevent unintended retries and invalid timer creation.
packages/durabletask-js/test/orchestration_executor.spec.ts	Adds coverage for invalid retry-handler returns and finite-delay retry behavior.