Add unit test coverage for pluginsFromRows in scripts/build-stats.mjs

[sakshar2303]

Resolves #271

Description

In scripts/build-stats.mjs, pluginsFromRows is responsible for parsing raw query results from PostHog, validating plugin IDs, dropping corrupt or invalid rows, and sorting keys to ensure byte-stable JSON generation for HTTP caching.

However, build-stats.mjs lacked automated unit test coverage because its row-parsing logic was defined inline and top-level network queries were evaluated immediately upon loading.

This PR:

1. Exports ENTRY_ID_PATTERN and pluginsFromRows from scripts/marketplace-lib.mjs (with an optional logger parameter so tests can suppress or assert warning logs cleanly).
2. Imports pluginsFromRows in scripts/build-stats.mjs.
3. Adds unit test coverage in test/marketplace.test.mjs testing:
   • Successful parsing of valid rows and preservation of lexicographical key ordering.
   • Dropping malformed rows, non-array rows, uppercase/invalid plugin IDs, non-safe integers, floats, negative install numbers, and non-numeric values.

Local Validation

• npm test (all 37 tests pass)
• npm run build
• npm run gate:v1