Fix long overflow in CosineSimilarity dot product

[PHJ2000]

Comparing identical vectors containing three Integer.MAX_VALUE components returns -0.33333333457509673 instead of 1.0. Each individual product fits in a long, but their sum overflows the long accumulator in CosineSimilarity.dot().

Accumulate the dot product in double, as the squared norms already do. Keep the long multiplication so each integer product is computed without integer overflow before accumulation. Add a parameterized regression test for identical vectors with components 1, Integer.MAX_VALUE, and Integer.MIN_VALUE.

Validation:

• On unmodified production code, mvn -Dtest=CosineSimilarityTest test ran 7 tests and failed the two large-value cases.
• The published 1.15.0 JAR also reproduces the positive-vector failure.
• After the change, the default mvn goal passes, including the full test suite, Apache RAT, japicmp, Checkstyle, PMD, SpotBugs, and Javadoc generation (OpenJDK 21.0.12.1, Maven 3.9.11).

Jira: pending an Apache Jira account. This PR remains a draft until the report can be filed and its issue key linked here and in the commit message.

Checklist from the repository template:

• Read the contribution guidelines.
• Read the ASF Generative Tooling Guidance.
• Used AI: OpenAI Codex investigated the bug, generated the implementation change and regression test, ran validation, and drafted the issue/PR text.
• Run a successful build using the default Maven goal (mvn).
• Added regression tests that fail without the production change.
• Explained what changes, how, and why.
• Used a meaningful commit subject and body.