[sdk/python] Stop advertising HTTP image URLs (#29464)

## Summary

- use generated image data URLs in the Python SDK examples and notebook
- document HTTP and HTTPS image URLs as deprecated and recommend
`LocalImageInput`
- replace the remote-URL integration test with data-URL coverage

`ImageInput` remains available for data URLs. The SDK does not duplicate
app-server URL validation.

## Testing

- `uv run --frozen --no-sync ruff check --output-format=full .`
- `uv run --frozen --no-sync ruff format --check .`
- full Python SDK test suite with an isolated writable
`CODEX_SQLITE_HOME` (119 passed, 38 skipped)

sdk/python/examples/07_image_and_text/async.py

@@ -5,7 +5,7 @@ _EXAMPLES_ROOT = Path(__file__).resolve().parents[1]
 if str(_EXAMPLES_ROOT) not in sys.path:
     sys.path.insert(0, str(_EXAMPLES_ROOT))
 
-from _bootstrap import ensure_local_sdk_src, runtime_config
+from _bootstrap import ensure_local_sdk_src, generated_sample_image_data_url, runtime_config
 
 ensure_local_sdk_src()
 
@@ -13,7 +13,7 @@ import asyncio
 
 from openai_codex import AsyncCodex, ImageInput, TextInput
 
-REMOTE_IMAGE_URL = "https://raw.githubusercontent.com/github/explore/main/topics/python/python.png"
+IMAGE_DATA_URL = generated_sample_image_data_url()
 
 
 async def main() -> None:
@@ -24,7 +24,7 @@ async def main() -> None:
         turn = await thread.turn(
             [
                 TextInput("What is in this image? Give 3 bullets."),
-                ImageInput(REMOTE_IMAGE_URL),
+                ImageInput(IMAGE_DATA_URL),
             ]
         )
         result = await turn.run()

sdk/python/examples/07_image_and_text/sync.py

@@ -5,20 +5,20 @@ _EXAMPLES_ROOT = Path(__file__).resolve().parents[1]
 if str(_EXAMPLES_ROOT) not in sys.path:
     sys.path.insert(0, str(_EXAMPLES_ROOT))
 
-from _bootstrap import ensure_local_sdk_src, runtime_config
+from _bootstrap import ensure_local_sdk_src, generated_sample_image_data_url, runtime_config
 
 ensure_local_sdk_src()
 
 from openai_codex import Codex, ImageInput, TextInput
 
-REMOTE_IMAGE_URL = "https://raw.githubusercontent.com/github/explore/main/topics/python/python.png"
+IMAGE_DATA_URL = generated_sample_image_data_url()
 
 with Codex(config=runtime_config()) as codex:
     thread = codex.thread_start(model="gpt-5.4", config={"model_reasoning_effort": "high"})
     result = thread.turn(
         [
             TextInput("What is in this image? Give 3 bullets."),
-            ImageInput(REMOTE_IMAGE_URL),
+            ImageInput(IMAGE_DATA_URL),
         ]
     ).run()
 

sdk/python/examples/README.md

@@ -72,7 +72,7 @@ python examples/01_quickstart_constructor/async.py
 - `06_thread_lifecycle_and_controls/`
   - thread lifecycle + control calls
 - `07_image_and_text/`
-  - remote image URL + text multimodal turn
+  - image data URL + text multimodal turn
 - `08_local_image_and_text/`
   - local image + text multimodal turn using a generated temporary sample image
 - `09_async_parity/`

sdk/python/examples/_bootstrap.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import base64
 import contextlib
 import importlib.util
 import sys
@@ -95,6 +96,11 @@ def _generated_sample_png_bytes() -> bytes:
     )
 
 
+def generated_sample_image_data_url() -> str:
+    encoded = base64.b64encode(_generated_sample_png_bytes()).decode("ascii")
+    return f"data:image/png;base64,{encoded}"
+
+
 @contextlib.contextmanager
 def temporary_sample_image_path() -> Iterator[Path]:
     with tempfile.TemporaryDirectory(prefix="codex-python-example-image-") as temp_root: