feat: add pipeline engine with approval flow and file triggers

Sequential step executor (script, claude_prompt, approval, api_call,
template, skyvern placeholder), reaction-based approvals, file upload
trigger matching, portal API state sync.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

pipelines/steps/__init__.py

@@ -0,0 +1,45 @@
+"""Step type registry and dispatcher."""
+
+import logging
+
+from .script import execute_script
+from .claude_prompt import execute_claude_prompt
+from .template import execute_template
+from .api_call import execute_api_call
+from .skyvern import execute_skyvern
+
+logger = logging.getLogger(__name__)
+
+STEP_EXECUTORS = {
+    "script": execute_script,
+    "claude_prompt": execute_claude_prompt,
+    "template": execute_template,
+    "api_call": execute_api_call,
+    "skyvern": execute_skyvern,
+}
+
+
+async def execute_step(
+    step_type: str,
+    step_config: dict,
+    context: dict,
+    send_text,
+    target_room: str,
+    llm=None,
+    default_model: str = "claude-haiku",
+    escalation_model: str = "claude-sonnet",
+) -> str:
+    """Execute a pipeline step and return its output as a string."""
+    executor = STEP_EXECUTORS.get(step_type)
+    if not executor:
+        raise ValueError(f"Unknown step type: {step_type}")
+
+    return await executor(
+        config=step_config,
+        context=context,
+        send_text=send_text,
+        target_room=target_room,
+        llm=llm,
+        default_model=default_model,
+        escalation_model=escalation_model,
+    )