fix: remove dead jiraBefore assignment (ineffassign)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: bschellenberger2600

internal/git/rain_test.go

@@ -277,10 +277,8 @@ func TestRainRepository_MainlineMode_UserPatternsExtendMainline(t *testing.T) {
 	testutil.RunGitCmd(t, peerDir, "commit", "-m", "jira advance")
 	testutil.RunGitCmd(t, peerDir, "push", "origin", "JIRA-123")
 
-	testutil.RunGitCmd(t, repo.Path(), "checkout", defaultBranch)
-	jiraBefore := testutil.GetCurrentSHA(t, repo.Path())
 	testutil.RunGitCmd(t, repo.Path(), "checkout", "JIRA-123")
-	jiraBefore = testutil.GetCurrentSHA(t, repo.Path())
+	jiraBefore := testutil.GetCurrentSHA(t, repo.Path())
 	testutil.RunGitCmd(t, repo.Path(), "checkout", defaultBranch)
 
 	result, err := RainRepository(repo.Path(), RainOptions{