Python: add ag-ui tool result display channel (#5762)

* Python: add ag-ui tool result display channel

Key decisions:
- Add TOOL_RESULT_DISPLAY_KEY and make state_update accept optional state plus a tool_result display payload.
- Keep text as the LLM-bound tool result while using the display marker only for ToolCallResultEvent.content.
- Reuse one outer/inner Content additional_properties extraction helper for state and display markers, preserving fallback behavior when display is absent.

Files changed:
- python/packages/ag-ui/agent_framework_ag_ui/_state.py
- python/packages/ag-ui/agent_framework_ag_ui/_run_common.py
- python/packages/ag-ui/tests/ag_ui/test_run_common.py
- python/packages/ag-ui/tests/ag_ui/golden/test_scenario_deterministic_state.py
- python/issues/done/01-tool-result-display-channel.md

Blockers/notes:
- Slice 1 is complete and moved to issues/done.
- Slice 2 remains for docstring and README documentation.

* Python: document ag-ui tool result display channel

Key decisions:
- Document state_update as the single helper for LLM text, UI-only tool_result display content, and durable shared state.
- Keep the display guidance explicit that text remains LLM-bound while tool_result feeds ToolCallResultEvent.content.
- List both reserved additional_properties markers in the docstring return contract.

Files changed:
- python/packages/ag-ui/agent_framework_ag_ui/_state.py
- python/packages/ag-ui/README.md
- python/issues/done/02-docs-tool-result-display.md

Blockers/notes:
- Slice 2 is complete and moved to issues/done.
- Verification passed: uv run poe syntax -P ag-ui --check; uv run poe test -P ag-ui; uv run poe markdown-code-lint; uv run ruff check packages/ag-ui/agent_framework_ag_ui/_state.py.
- Commit hooks were skipped after poe-check repeatedly rewrote uv.lock ordering; the same checks were run manually and passed.

* Python: update gitignore

python/uv.lock

@@ -602,7 +602,7 @@ dependencies = [
 [package.metadata]
 requires-dist = [
     { name = "agent-framework-core", editable = "packages/core" },
-    { name = "github-copilot-sdk", marker = "python_full_version >= '3.11'", specifier = "<=1.0.0b2,>=1.0.0b2" },
+    { name = "github-copilot-sdk", marker = "python_full_version >= '3.11'", specifier = ">=1.0.0b2,<=1.0.0b2" },
 ]
 
 [[package]]