fix(agent): Switch no longer matches an empty condition (all([]) is True) (#15644)

## Summary
Fixes the agent `Switch` component matching an **empty/all-skipped
condition** unconditionally because `all([]) is True`.

## Root cause
`res` only accumulates for items with a non-empty `cpn_id` (blank ones
`continue`). For a condition with empty `items` (or all-blank `cpn_id`),
`res == []`, and `if all(res):` is `True`, so the Switch routes to that
condition's `to` target before reaching the else/`end_cpn_ids` branch.

## Fix
```diff
-            if all(res):
+            if res and all(res):
```
An empty result set no longer counts as a match; genuinely-satisfied
"and" conditions still route (the real `all(res)` path is preserved).

## Files changed
- `agent/component/switch.py`
- `test/unit_test/agent/component/test_switch_empty_condition.py` (new)

## Verification
- `ruff check` / `ruff format --check` — clean
- Added unit tests (mirroring the existing `_FakeCanvas` component-test
pattern): an empty/all-skipped "and" condition now falls through to
`end_cpn_ids`; a genuinely-satisfied "and" condition still routes to its
target.
- Local full pytest not run (heavy RAG deps); CI validates.

## Note
Implemented with LLM assistance (model: claude-opus-4-8).

Closes #15643

---------

Co-authored-by: seekmistar01 <seekmistar01@users.noreply.github.com>
Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Co-authored-by: Zhichang Yu <yuzhichang@gmail.com>

test/unit_test/agent/component/test_switch_empty_condition.py

@@ -0,0 +1,94 @@
+#
+#  Copyright 2025 The InfiniFlow Authors. All Rights Reserved.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+
+"""Unit tests for ``Switch`` condition evaluation.
+
+Regression: an "and" condition whose ``items`` are all skipped (empty
+``cpn_id``) leaves the per-condition result list empty, and ``all([]) is True``,
+so the Switch matched that condition unconditionally and routed to it before
+ever reaching the else/end branch.
+"""
+
+from types import SimpleNamespace
+
+import pytest
+
+from agent.component.switch import Switch
+
+
+pytestmark = [pytest.mark.p1]
+
+
+class _FakeCanvas:
+    def __init__(self, refs=None):
+        self._refs = refs or {}
+
+    def get_variable_value(self, token):
+        return self._refs.get(token)
+
+    def get_component_name(self, cpn_id):
+        return cpn_id
+
+
+def _make_switch(conditions, end_cpn_ids, refs=None):
+    sw = Switch.__new__(Switch)
+    sw._param = SimpleNamespace(conditions=conditions, end_cpn_ids=end_cpn_ids)
+    sw._canvas = _FakeCanvas(refs)
+    sw.check_if_canceled = lambda _msg: False
+    sw.set_input_value = lambda *_args, **_kwargs: None
+    outputs = {}
+    sw.set_output = lambda key, value: outputs.__setitem__(key, value)
+    sw._invoke()
+    return outputs
+
+
+def test_empty_condition_falls_through_to_end():
+    # The only item is skipped (blank cpn_id) -> result list is empty.
+    conditions = [
+        {
+            "logical_operator": "and",
+            "items": [{"cpn_id": "", "operator": "contains", "value": "x"}],
+            "to": ["TARGET"],
+        }
+    ]
+    outputs = _make_switch(conditions, end_cpn_ids=["END"])
+    assert outputs["_next"] == ["END"]
+
+
+def test_empty_and_items_fall_through_to_end():
+    conditions = [
+        {
+            "logical_operator": "and",
+            "items": [],
+            "to": ["TARGET"],
+        }
+    ]
+    outputs = _make_switch(conditions, end_cpn_ids=["END"])
+    assert outputs["_next"] == ["END"]
+
+
+def test_satisfied_and_condition_still_routes():
+    # A genuinely satisfied "and" condition must still route to its target
+    # (the fix must not break the real all(res) path).
+    conditions = [
+        {
+            "logical_operator": "and",
+            "items": [{"cpn_id": "c@out", "operator": "contains", "value": "hello"}],
+            "to": ["TARGET"],
+        }
+    ]
+    outputs = _make_switch(conditions, end_cpn_ids=["END"], refs={"c@out": "hello world"})
+    assert outputs["_next"] == ["TARGET"]