python-sdk: expose canonical app-server types (2026-03-16)

Remove the SDK alias/result layers so the wrapper surface returns canonical generated app-server models directly.

- delete public type alias modules and regenerate v2_all.py against current schema
- return InitializeResponse from metadata and generated Turn from run()
- update docs, examples, notebook, and tests to use canonical generated models and repo-only text extraction helpers

Validation:
- PYTHONPATH=sdk/python/src python3 -m pytest sdk/python/tests
- GH_TOKEN="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" RUN_REAL_CODEX_TESTS=1 PYTHONPATH=sdk/python/src python3 -m pytest sdk/python/tests -rs

Co-authored-by: Codex <noreply@openai.com>

sdk/python/tests/test_public_api_signatures.py

@@ -196,15 +196,15 @@ def test_lifecycle_methods_are_codex_scoped() -> None:
 
 
 def test_initialize_metadata_parses_user_agent_shape() -> None:
-    parsed = Codex._parse_initialize(InitializeResponse.model_validate({"userAgent": "codex-cli/1.2.3"}))
-    assert parsed.user_agent == "codex-cli/1.2.3"
-    assert parsed.server_name == "codex-cli"
-    assert parsed.server_version == "1.2.3"
+    payload = InitializeResponse.model_validate({"userAgent": "codex-cli/1.2.3"})
+    parsed = Codex._validate_initialize(payload)
+    assert parsed is payload
+    assert parsed.userAgent == "codex-cli/1.2.3"
 
 
 def test_initialize_metadata_requires_non_empty_information() -> None:
     try:
-        Codex._parse_initialize(InitializeResponse.model_validate({}))
+        Codex._validate_initialize(InitializeResponse.model_validate({}))
     except RuntimeError as exc:
         assert "missing required metadata" in str(exc)
     else: