fix: validate batch size option

[marandaneto]

💡 Motivation and Context

Invalid batch_size values such as 0 or negative numbers could make queued consumers flush with a non-positive batch size. This hardens the option so non-positive values keep the default batch size, while documenting the intended queue behavior with parameterized tests.

💚 How did you test it?

• ./vendor/bin/phpunit --no-coverage test/PostHogTest.php --filter 'CapturesStayQueued|BatchSizeOne'
• ./vendor/bin/phpunit --no-coverage test/PostHogTest.php
• ./vendor/bin/phpunit --no-coverage
• git diff --check
• ./vendor/bin/phpcs lib/QueueConsumer.php

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

If releasing new changes

• Ran pnpm changeset to generate a changeset file

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Implemented with Pi coding agent assistance. The change keeps the queue consumer behavior minimal: valid positive batch_size values still apply, while invalid non-positive values fall back to the existing default. Tests cover default batching, invalid non-positive batch_size fallback behavior, and immediate flushing with batch_size => 1; review feedback was addressed by parameterizing the shared queued-until-flush cases.

[greptile-apps]

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

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### Issue 1 of 1
test/PostHogTest.php:379-412
**Prefer parameterised tests for related queue-behavior scenarios**

`testLowVolumeCapturesStayQueuedUntilFlush` and `testInvalidBatchSizeUsesDefault` share identical assertion logic (one capture, zero HTTP calls before flush, one `/batch/` call after explicit flush). The only structural difference is the options array. Folding the default-batch-size case into the `invalidBatchSizeCases` provider — or creating a combined provider that also covers the `null`/omitted `batch_size` scenario — would express this as OnceAndOnlyOnce and make any future queue-behavior change a single edit. `testBatchSizeOneFlushesImmediately` tests a meaningfully different observable outcome (auto-flush) and is fine as a standalone, or could itself become a named entry in a provider keyed on `[batch_size, expectsImmediateFlush]`.

_{Reviews (1): Last reviewed commit: "fix: validate batch size option" | Re-trigger Greptile}