feat: add token bucket rate limiter

[dsm20]

Adds a rate limiter module with Express middleware support for testing comprehension gate e2e.

[github-actions]

Comprehension Gate

Answer the questions below in order to merge.

Q1. What is the primary reason for adding reactions (eyes, rocket, confused) to comments in check.mjs?

• A) To provide a visual indicator of the PR author's emotional state regarding the comprehension gate.
• B) To give immediate, at-a-glance feedback on the status of the comprehension gate check for a given comment.
• C) To trigger specific actions in other GitHub workflows based on the reaction type.
• D) To allow external monitoring tools to easily track the progress of comprehension gate checks.

Q2. The TokenBucketRateLimiter initializes a new bucket for a clientId when tryConsume is called and either no bucket exists or the existing bucket's windowStart is outside the current window. In this scenario, how many tokens are initially assigned to the new bucket?

• A) 1 less than maxRequests.
• B) Equal to maxRequests.
• C) 0, as the first request consumes the initial token.
• D) A random number between 1 and maxRequests.

Q3. What is the purpose of the cleanup method in TokenBucketRateLimiter and its associated setInterval call in createMiddleware?

• A) To reset all client buckets to their maxRequests limit after a fixed interval, ensuring fair usage.
• B) To log the current state of all rate limiter buckets for debugging purposes.
• C) To automatically adjust the windowMs and maxRequests parameters based on observed traffic patterns.
• D) To remove stale client buckets that haven't been accessed for an extended period, preventing memory leaks.

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Reply in a format like this:

1. A
2. C
3. B

Questions are based on commit 565edbb. Pushing new commits regenerates the questions.

[dsm20]

1. B
2. A
3. D

[github-actions]

Comprehension Gate — INCORRECT

Score: 2/3 | Q1: PASS | Q2: PASS | Q3: FAIL (you answered C)

Please re-read the flagged parts of the diff and submit a new comment with corrected answers.

[dsm20]

1. B
2. A
3. D

[github-actions]

Comprehension Gate — PASSED

Score: 3/3 | Q1: PASS | Q2: PASS | Q3: PASS

Comprehension gate passed — this PR is cleared to merge.

[dsm20]

1. B
2. A
3. D

[github-actions]

Comprehension Gate — PASSED

Score: 3/3 | Q1: PASS | Q2: PASS | Q3: PASS

Comprehension gate passed — this PR is cleared to merge.