Python: .NET: Harden argument scoping for standing approval rules in ToolApprovalAgent

[rogerbarreto]

Summary

Review and harden how ToolApprovalAgent records and matches standing approval rules in Microsoft.Agents.AI (dotnet/src/Microsoft.Agents.AI/Harness/ToolApproval/). The goal is to ensure an argument-scoped standing approval stays scoped exactly as the user intended for all argument shapes, and that the .NET behavior matches the existing Python implementation in agent_framework/_harness/_tool_approval.py.

Scope

• ToolApprovalAgent.cs, ToolApprovalRule.cs, ToolApprovalRequestContentExtensions.cs
• Align the argument-normalization/matching contract with the Python harness, whose ToolApprovalRule semantics already document the intended behavior.

Acceptance criteria

• Argument-scoped standing approvals match only the intended calls across all argument shapes.
• Behavior is consistent between the .NET and Python tool-approval harnesses.
• Regression tests cover the standing-rule argument-matching paths.