fix(workflows): address Copilot review feedback on continue_on_error

- Reword README "Error Handling" intro in terms of `StepStatus.FAILED`
  halting by default, with non-zero shell/command exit as one common
  cause. Avoids implying only exit codes can halt a run (gate aborts
  and validation failures also do, just via different mechanisms).
- Tighten `test_validation_accepts_bool_continue_on_error` to assert
  `errors == []` instead of "no error mentions continue_on_error", so
  unrelated validation regressions on the same minimal YAML can no
  longer slip past this test.
- In `test_gate_abort_still_halts_with_continue_on_error`, swap
  `sys.stdin` itself for a stub `_TTYStdin` instead of patching
  `sys.stdin.isatty`. Method-on-instance assignment is unreliable on
  real `io.TextIOWrapper` objects (e.g. under pytest with capture
  disabled), so replacing the whole stdin object is more robust
  across runners.

All 2967 tests still pass.

Author: doquanghuy

tests/test_workflows.py

@@ -2322,7 +2322,14 @@ def test_gate_abort_still_halts_with_continue_on_error(
         # Force the gate step into interactive mode and feed a "reject"
         # choice so the abort path actually runs in the test env
         # (default behaviour returns PAUSED when stdin is not a TTY).
-        monkeypatch.setattr(gate_module.sys.stdin, "isatty", lambda: True)
+        # Swap sys.stdin itself for a stub: setattr on the real
+        # TextIOWrapper's `isatty` method is not assignable under some
+        # runners (e.g. pytest with capture disabled).
+        class _TTYStdin:
+            def isatty(self) -> bool:
+                return True
+
+        monkeypatch.setattr(gate_module.sys, "stdin", _TTYStdin())
         monkeypatch.setattr(
             GateStep, "_prompt", staticmethod(lambda _msg, _opts: "reject")
         )
@@ -2399,9 +2406,7 @@ def test_validation_accepts_bool_continue_on_error(self):
     continue_on_error: {yaml_value}
 """)
             errors = validate_workflow(definition)
-            assert not any(
-                "continue_on_error" in e for e in errors
-            ), errors
+            assert errors == [], errors
 
 
 # ===== State Persistence Tests =====

workflows/README.md

@@ -221,11 +221,14 @@ Aggregate results from fan-out steps:
 
 ## Error Handling
 
-By default, a non-zero exit code from any step halts the entire run.
-Set `continue_on_error: true` on a step to record its result and
-continue to the next sibling step instead. The exit code remains
-available on `steps.<id>.output.exit_code` so downstream `if`,
-`switch`, or `gate` steps can branch on it:
+By default, any step that ends in `StepStatus.FAILED` halts the entire
+run — most commonly a `shell` or `command` step exiting non-zero, but
+also things like a step type that fails validation. Set
+`continue_on_error: true` on a step to record its result and continue
+to the next sibling step instead. When the failure was a non-zero
+exit, the exit code remains available on
+`steps.<id>.output.exit_code` so downstream `if`, `switch`, or `gate`
+steps can branch on it:
 
 ```yaml
 - id: heavy-thing