Fix main signature to match control flow and harden CLI path tests

[LqauzDev]

This PR makes two small but important correctness fixes without changing behavior.

First, main no longer advertises a Result return type while unconditionally terminating the process on errors. Since the error path always calls process::exit, the function never returns Err, so the previous signature was basically misleading. The updated signature reflects the actual control flow and avoids implying Rust-managed error propagation that never happens.

Second, the CLI test assertions were tightened to avoid string-based path comparisons. The test now compares Path values directly, removing assumptions about UTF-8 encoding and path formatting while keeping the same intent and coverage.

[jonathanmagambo]

thank you so much