perf(resolve): avoid re-parsing files in build_suggestion_hint

[rocketman-code]

When resolve_targets returns NoTargetsFound, build_suggestion_hint re-reads and re-parses every .rs file via extract_functions. These files were already parsed during the spec-matching loop.

This is on the error path only, so it does not affect happy-path performance. For very large codebases, it doubles I/O and syn parsing work on failure.

Potential fix: collect function names during the initial resolution pass and pass them into build_suggestion_hint, avoiding the second parse.