fix execEvenlyMinDelayMs not reflecting points/duration mutation

[quad]

The setter evaluated the default at first assignment and cached it, so
runtime updates to points or duration left the spacing computed from
construction-time values. The docs state that options can be changed at
runtime; this brings execEvenlyMinDelayMs in line with that contract.

Now: if execEvenlyMinDelayMs was never explicitly set, the getter
derives it from the current msDuration/points on each read. Explicit
values are still honoured.

[Copilot]

Pull request overview

Note

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Updates execEvenlyMinDelayMs to be lazily derived from current points/duration unless explicitly set, and adds tests to ensure the derived value updates when inputs are mutated.

Changes:

• Make execEvenlyMinDelayMs getter derive from msDuration / points when no explicit value is set.
• Simplify execEvenlyMinDelayMs setter to store the provided value as-is.
• Add unit tests covering re-derivation behavior when points/duration are mutated.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 3 comments.

File	Description
test/RateLimiterAbstract.test.js	Adds tests validating derived vs explicit execEvenlyMinDelayMs behavior under mutation.
lib/RateLimiterAbstract.js	Changes execEvenlyMinDelayMs to be computed dynamically unless explicitly set.

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[animir]

@quad Hey. Looks good to me. I've added some guards for edge cases. Thanks.