Feat: Refact pipeline (#13826)

### What problem does this PR solve?

### Type of change

- [x] New Feature (non-breaking change which adds functionality)
- [x] Refactoring

---------

Co-authored-by: Zhichang Yu <yuzhichang@gmail.com>
Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

test/testcases/test_web_api/test_canvas_app/test_canvas_routes_unit.py

@@ -442,7 +442,10 @@ def _load_canvas_module(monkeypatch):
 
     agent_pkg = ModuleType("agent")
     agent_pkg.__path__ = []
+    agent_dsl_migration_mod = ModuleType("agent.dsl_migration")
+    agent_dsl_migration_mod.normalize_chunker_dsl = lambda dsl: dsl
     monkeypatch.setitem(sys.modules, "agent", agent_pkg)
+    monkeypatch.setitem(sys.modules, "agent.dsl_migration", agent_dsl_migration_mod)
 
     agent_component_mod = ModuleType("agent.component")
 
@@ -450,6 +453,7 @@ def _load_canvas_module(monkeypatch):
         pass
 
     agent_component_mod.LLM = _StubLLM
+    agent_pkg.component = agent_component_mod
     monkeypatch.setitem(sys.modules, "agent.component", agent_component_mod)
 
     agent_canvas_mod = ModuleType("agent.canvas")
@@ -479,6 +483,8 @@ def _load_canvas_module(monkeypatch):
             return "{}"
 
     agent_canvas_mod.Canvas = _StubCanvas
+    agent_pkg.canvas = agent_canvas_mod
+    agent_pkg.dsl_migration = agent_dsl_migration_mod
     monkeypatch.setitem(sys.modules, "agent.canvas", agent_canvas_mod)
 
     quart_mod = ModuleType("quart")