fix(showcase): claude-sdk-python missing openai dep crashed agent on import

Root cause: src/agents/a2ui_dynamic.py imported `openai` at module top
level, but openai was not in requirements.txt. The agent_server.py imports
a2ui_dynamic at top level too, so on container startup the entire FastAPI
module failed to load with ModuleNotFoundError. entrypoint.sh's startup
gate ("Agent failed to start - exiting") then bailed before Next.js
launched, taking the whole container down. Railway's restart loop made
every /demos/<id> route unreachable, which is exactly the symptom the
D2 e2e-readiness probe reports as red across all 9 features in this
framework column.

Two-part fix:
- Add openai>=1.50.0 to requirements.txt so the dep is actually
  installed in the agent-builder stage.
- Move the `import openai` to a lazy import inside _generate_a2ui
  (mirroring the same pattern in agents/agent.py:339), so a future
  requirements regression localizes the failure to the one
  declarative-gen-ui demo instead of nuking the whole backend on
  module load.

Author: AlemTuzlak

showcase/integrations/claude-sdk-python/requirements.txt

@@ -6,3 +6,12 @@ python-dotenv>=1.0.1
 # Used by the multimodal demo to flatten PDFs to text so the model can
 # read them without depending on Claude's PDF beta.
 pypdf>=4.0.0
+# Used by the declarative-gen-ui demo (a2ui_dynamic.py) for the secondary
+# LLM bound to the render_a2ui tool. Imported at module top of
+# agents/a2ui_dynamic.py — without it the entire agent_server module fails
+# to load on container startup, taking the FastAPI backend down. The
+# entrypoint then exits before Next.js launches, making every demo route
+# unreachable (D2 e2e-readiness goes red across the board). Lazy-importing
+# inside _generate_a2ui would localize the failure but `requirements.txt`
+# is the right place to declare the runtime dep.
+openai>=1.50.0

showcase/integrations/claude-sdk-python/src/agents/a2ui_dynamic.py

@@ -24,7 +24,6 @@
 from typing import Any
 
 import anthropic
-import openai
 from ag_ui.core import (
     EventType,
     RunAgentInput,
@@ -83,6 +82,13 @@
 
 def _generate_a2ui(context: str, conversation_messages: list[dict[str, Any]] | None = None) -> dict[str, Any]:
     """Invoke a secondary LLM bound to render_a2ui and return an operations container."""
+    # Lazy-import openai so a missing/uninstalled dep doesn't take the entire
+    # agent_server module down at import time — that import-time failure
+    # cascades through entrypoint.sh ("Agent failed to start — exiting")
+    # and prevents Next.js from booting, making every demo route in this
+    # integration unreachable. Mirrors the same lazy-import pattern in
+    # agents/agent.py:339 for the shared `generate_a2ui` tool handler.
+    import openai
     client = openai.OpenAI()
     llm_messages: list[dict[str, Any]] = [
         {"role": "system", "content": context or "Generate a useful dashboard UI."},