chore: improve installer maintenance path

[lphuc2250gma]

Summary:

• Add a focused unit test in tests/test_utils.py that exercises an edge case of installer.utils.parse_entrypoints (e.g., entries with surrounding whitespace, comments, or duplicate group headers) to lock in current behavior; if the function lacks explicit handling for one of these, add a minimal narrow assertion/guard in src/installer/utils.py rather than restructuring it.
• Keep the change narrow so it is straightforward to review.

Notes:

• I kept this scoped to the relevant implementation and tests.