fix(terminal): avoid merging heredoc EOF with fence wrapper (#3598)

One-shot local execution built `printf FENCE; <cmd>; __hermes_rc=...`, so a
command ending in a heredoc produced a closing line like `EOF; __hermes_rc=...`,
which is not a valid delimiter. Bash then treated the rest of the wrapper as
heredoc body, leaking it into tool output (e.g. gh issue/PR flows).

Use newline-separated wrapper lines so the delimiter stays alone and the
trailer runs after the heredoc completes.

Co-authored-by: kshitijk4poor <82637225+kshitijk4poor@users.noreply.github.com>

tests/tools/test_local_persistent.py

@@ -63,6 +63,18 @@ class TestLocalOneShotRegression:
         assert r["output"].strip() == ""
         env.cleanup()
 
+    def test_oneshot_heredoc_does_not_leak_fence_wrapper(self):
+        """Heredoc closing line must not be merged with the fence wrapper tail."""
+        env = LocalEnvironment(persistent=False)
+        cmd = "cat <<'H_EOF'\nheredoc body line\nH_EOF"
+        r = env.execute(cmd)
+        env.cleanup()
+        assert r["returncode"] == 0
+        assert "heredoc body line" in r["output"]
+        assert "__hermes_rc" not in r["output"]
+        assert "printf '" not in r["output"]
+        assert "exit $" not in r["output"]
+
 
 class TestLocalPersistent:
     @pytest.fixture