test(coverage): add targeted tests to raise per-package coverage gates

- internal/homesick/version: new version_test.go covers String constant
  and semver format validation
- internal/homesick/cli: add list, generate, clone, status, diff, and
  git-repo helper tests; coverage raised from 62.5% to 71.2%
- internal/homesick/core: new helpers_test.go covers runGit pretend,
  actionVerb, sayStatus, unlinkPath, linkPath, readSubdirs,
  matchesIgnoredDir, confirmDestroy, ExecAll edge cases, and
  Link/Unlink default castle wrappers; core_test.go and pull_test.go
  extended with New constructor and PullAll quiet-mode tests;
  exec_test.go extended with ExecAll no-repos-dir and error-wrap tests;
  coverage raised from 75.6% to 80.2%

internal/homesick/core/pull_test.go

@@ -140,3 +140,17 @@ func (s *PullSuite) TestPullAll_PrintsCastlePrefixes() {
 	require.Contains(s.T(), stdout.String(), "alpha:")
 	require.Contains(s.T(), stdout.String(), "zeta:")
 }
+
+func (s *PullSuite) TestPullAll_QuietSuppressesCastlePrefixes() {
+	require.NoError(s.T(), os.MkdirAll(filepath.Join(s.reposDir, "alpha", ".git"), 0o755))
+	require.NoError(s.T(), os.MkdirAll(filepath.Join(s.reposDir, "zeta", ".git"), 0o755))
+
+	stdout := &bytes.Buffer{}
+	s.app.Stdout = stdout
+	s.app.Quiet = true
+	s.app.Pretend = true
+
+	require.NoError(s.T(), s.app.PullAll())
+	require.NotContains(s.T(), stdout.String(), "alpha:")
+	require.NotContains(s.T(), stdout.String(), "zeta:")
+}