bug: concurrency detection warnings printed twice per function

[rocketman-code]

Summary

Concurrency detection warnings ("spawns parallel work -- add --cpu-time to see computation time") are printed twice for each detected function.

Reproduction

Observed on multiple projects during 0.13.0 QA panel:

• just (casey/just): 62 warnings total, each function warned twice
• tokei (XAMPPRocky/tokei): 10 warnings, each printed twice

Expected

Each function should produce at most one warning.

Impact

P3 — cosmetic/UX. The wall of duplicate warnings is noisy and overwhelming for first-time users, especially on large codebases.