fix: correctness lens emoji ✅ -> 🎯 (✅ read like 'no issues')

A green check on a section reporting blocking issues was misleading; 🎯 signals
accuracy/on-target. Section verdict text already conveys pass/fail.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

cmd/gadfly/specialists.go

@@ -27,7 +27,7 @@ var builtinSpecialists = map[string]Specialist{
 		"Authn/authz gaps, injection (SQL/command/path/template), SSRF, unsafe deserialization, " +
 		"secret/credential leakage, missing input validation, unsafe handling of untrusted data, " +
 		"and insecure defaults. Trace tainted input to where it's used."},
-	"correctness": {"correctness", "✅ Correctness", "" +
+	"correctness": {"correctness", "🎯 Correctness", "" +
 		"Logic bugs and incorrect behavior introduced by the change. Pay special attention to " +
 		"SEMANTIC / domain correctness: do NOT trust a constant, conversion factor, formula, unit, " +
 		"or threshold because it looks reasonable — independently RE-DERIVE the expected value from " +