Teams CreateChat cannot create a self-only named group chat

## Issue Description

The Azure SRE Agent Teams connector cannot create a named group chat containing only the signed-in user. The operation implicitly appends that user, so neither explicitly supplying the user nor leaving the members input empty can produce the Graph-supported self-only group-chat shape.

## Steps to Reproduce

1. Configure the Microsoft Teams connector in Azure SRE Agent.
2. Call CreateChat with a topic and the signed-in user's Entra object ID in item.members.
3. Observe 400 BadRequest: "Duplicate chat members is specified in the request body."
4. Call CreateChat with item.members empty.
5. Observe 400 BadRequest indicating user@odata.bind is missing.

## Expected Behavior

CreateChat should support chatType=group with a topic and exactly one member. It should accept a structured Graph members array, and either deduplicate the signed-in user or expose autoIncludeSignedInUser=false. It should not add a bot, application, or additional user, and should return the created chat ID while preserving compatibility with existing semicolon-separated members input.

## Actual Behavior

CreateChat implicitly appends the signed-in user. Explicitly supplying that user creates a duplicate-member error; omitting members creates a missing user binding error. Therefore a self-only named group chat cannot be created through the connector.

Start at the Teams connector's CreateChat entry point and trace how the signed-in user and item.members are converted into the Microsoft Graph chat request. Reproduce both reported 400 responses, then verify the chosen behavior supports a self-only named group chat while preserving semicolon-separated members input and returning the created chat ID.

Written by the indexing model from the issue text.