bug: fix logging glitches (newline in discovery; duplicate build-system line)

[krystophny]

Category: bug
Priority: P2

PROBLEM: CLI output has formatting glitches/duplication.

EVIDENCE:

• "FortCov: Discovery returned 249\n files" (newline before 'files')
• Duplicate "📦 Build system detected: fpm" lines at start

SOLUTION:

• Fix string formatting and ensure single detection log
• Add smoke test for clean logs