Add comprehensive tests and improve type safety for array utilities

[pavankumar-vh]

Bug Fix:

• Fix loose 'any[]' typing in groupConsecutive function
• Add proper Group type definition for improved type safety
• This prevents type-related bugs when using the return value

Tests Added:

• Add 28 comprehensive tests covering all three utility functions
• filterDefined: 6 tests for null/undefined filtering with edge cases
• buildArray: 10 tests for array flattening and falsy value removal
• groupConsecutive: 12 tests for grouping logic with complex key functions
• All tests pass with 100% coverage of the utility functions

Scope: common/ (approved contribution area)

[codebuff-team]

Nice first contribution. The core fix in array.ts is correct and minimal: replacing any[] with a proper Group<T, U> type on groupConsecutive is a real improvement — it means callers now get typed key/items instead of any, which will surface bugs at compile time. No behavior change, so it's essentially risk-free to port.

The test file is thorough and well-organized (filterDefined, buildArray, groupConsecutive each covered with sensible edge cases: empty arrays, all-falsy, nested flattening, deep-equality grouping via isEqual). This is exactly the kind of coverage common/src/util was missing.

A couple of minor nits a maintainer may want addressed before porting:

• The Group type is defined inline inside the function; consider hoisting it to a named exported type (Group<T, U>) since it's a natural public type for callers of groupConsecutive.
• The last test (handles objects with deep equality) only asserts lengths, not full object equality — could tighten with a full toEqual check for completeness, though it's not blocking.

Overall this is exactly the shape of PR that's easy to review and easy to port: small semantic diff, tests added in the same directory as the source, no dependency or API changes. Good work — happy to see this land.