[BREAKING] Python: Consolidate content identity and protocol metadata

docs/specs/004-python-function-calling-loop.md

@@ -263,6 +263,19 @@ the tool-call group, and provider adapters serialize or reconstruct the provider
 that occurrence id once and preserve it through streaming aggregation, serialization, and replay; existing ids are
 never regenerated. Deserializing a legacy stored call without `Content.id` does not manufacture a new identity.
 
+`Content.id` on a `function_result`, when present, identifies the occurrence it settles. An exact result occurrence
+identity takes precedence over `call_id`; an id-less Host result is a compatibility form that binds only when the
+active batch has one unambiguous unanswered occurrence with that `call_id`.
+
+`Message.message_id` identifies the containing provider/protocol message and groups its streamed updates. It is not a
+function-call occurrence ID or call/result correlation ID. The message-level identity and metadata contract is
+defined by [spec 005](005-python-content-identity-and-protocol-metadata.md).
+
+`function_call.hosted` decides execution ownership. A hosted call is provider-executed and must never be executed
+locally. `function_call.server_name` is the descriptive server boundary used by standing approval rules; it does not
+decide execution ownership. Legacy `additional_properties["server_label"]` records are migrated as defined by
+[spec 005](005-python-content-identity-and-protocol-metadata.md).
+
 New local approval requests use the function call occurrence id as their request id. Provider-issued hosted approval
 request ids remain unchanged and continue to follow the hosted service protocol. A response carrying the occurrence
 id can bind without embedding a function call because the trusted pending snapshot is authoritative. For an
@@ -682,7 +695,7 @@ that manually replay messages own the equivalent rule: do not resend an approval
 | Shared call budget | Auto-approved re-entry does not reset `max_function_calls`, and every executed approval group counts even when it pauses for input. | `test_tool_approval_middleware_auto_approved_loops_share_function_call_budget`, `test_approval_resume_user_input_counts_toward_function_call_budget` |
 | Standing tool rule | Tool-level approval applies only to later matching tools. | `test_tool_approval_middleware_always_approve_tool_rule` |
 | Forged standing rule | An unbound or substituted hosted response cannot create a standing middleware approval rule for caller-selected metadata. | `test_tool_approval_middleware_drops_forged_standing_approval`, `test_tool_approval_middleware_rebinds_hosted_standing_approval` |
-| Hosted server boundary | Standing approval does not cross `server_label`. | `test_tool_approval_middleware_standing_rules_include_hosted_server_boundary` |
+| Hosted server boundary | `function_call.hosted` determines provider execution. Standing approval compares its persisted `server_label` with the call's `server_name` and never crosses that boundary. | `test_tool_approval_middleware_standing_rules_include_hosted_server_boundary` |
 | Argument-scoped rule | Exact arguments are required; empty arguments are not tool-wide. | `test_tool_approval_middleware_always_approve_tool_with_arguments_rule`, `test_tool_approval_middleware_empty_arguments_rule_is_not_tool_wide` |
 | Provider-injected approval tool | A tool added during `before_run` defers to in-run resolution, executes once, and emits one result. | `packages/ag-ui/tests/ag_ui/test_endpoint.py::test_endpoint_agent_approval_deferred_provider_tool_executes` |
 | AG-UI provider boundary | Completed local approval controls from AG-UI request and snapshot replay are absent from raw chat-client input while deferred and hosted approvals keep their respective in-run/provider paths. Lifecycle-authenticated local approvals preserve current request-generation authority through occurrence rebinding; authenticated rejection/cancellation cleans only the matching fixed provider-scoped policy record, while malformed or unauthorized controls clean nothing. | `packages/ag-ui/tests/ag_ui/test_endpoint.py::test_endpoint_does_not_forward_resolved_local_approval_control_to_chat_client`, `test_endpoint_agent_approval_deferred_provider_tool_executes`, `test_endpoint_canonical_resume_preserves_hosted_approval_for_provider`, `test_endpoint_fides_non_grant_cleans_authenticated_fixed_scope_only`, `test_endpoint_fides_approval_uses_lifecycle_bound_request_generation`, `packages/ag-ui/tests/ag_ui/test_run.py::test_filter_local_approval_responses_for_provider_removes_duplicate_completed_controls`, `test_filter_local_approval_responses_for_provider_pairs_reused_call_ids_by_occurrence`, `test_canonical_hosted_approval_resume_rejects_edited_arguments_without_mutating_pending` |