fix: harden and simplify Linux system install

Tighten shim detection, profile repair, and install ordering while
trimming over-specific doctor/info hints from the system-install path.

Co-authored-by: Cursor <cursoragent@cursor.com>

cmd/setup/doctor_system_test.go

@@ -0,0 +1,23 @@
+package setup
+
+import (
+	"testing"
+
+	"github.com/safedep/pmg/internal/doctor"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestPathContainsDir(t *testing.T) {
+	assert.True(t, pathContainsDir([]string{"/usr/local/lib/pmg/bin/"}, "/usr/local/lib/pmg/bin"))
+	assert.False(t, pathContainsDir([]string{"/usr/local/bin"}, "/usr/local/lib/pmg/bin"))
+	assert.False(t, pathContainsDir([]string{"/usr/bin"}, ""))
+}
+
+func TestSystemShimsWithoutPathDoNotActivateInterception(t *testing.T) {
+	results := []doctor.CheckResult{
+		{Name: checkShellAliases, Status: doctor.StatusWarn},
+		{Name: checkShimInPath, Status: doctor.StatusFail},
+	}
+
+	assert.False(t, isInterceptionActive(results))
+}