.NET: document host-owned telemetry and message content controls

[Naveen Chatlapalli (1aifanatic)]

Motivation & Context

The .NET portion of #8412 needs evidence about existing controls before introducing an API modeled on Python instrumentation. Applications also need to preserve telemetry providers and exporters owned by their host.

Description & Review Guide

• What are the major changes? Document the .NET UseOpenTelemetry entry point, explicit EnableSensitiveData=false configuration, host source/meter subscriptions, and configuration of separately instrumented chat clients.
• What is the impact of these changes? Clarifies existing content-capture controls without adding API or changing defaults. Explicitly distinguishes suppressing raw content from disabling event emission, and identifies the demo's existing sensitive-data opt-ins.
• What do you want reviewers to focus on? Confirm the intended .NET Microsoft OTel Distro package/signal and whether additional event suppression is required. This PR supplies the existing-control investigation; it does not assert distro-specific equivalence or close the unresolved integration requirement. All 51 OpenTelemetryAgentTests passed on net10.0, including streaming/non-streaming content-capture propagation. No live distro/exporter integration was exercised.

Related Issue

Contributes to #8444; deliberately leaves it open pending maintainer confirmation of the distribution-specific requirement. No other open .NET PR for this issue was found. Python changes in #8451 are separate.

Contribution Checklist

• The code builds clean without any errors or warnings
• All unit tests pass, and I have added new tests where possible
• The PR follows the Contribution Guidelines
• This PR is linked to an issue and there is no other open PR for this issue (see Related Issue above).
• This is not a breaking change.

[Copilot]

🟡 Changes recommended

Identify the meter name required by AddMeter and distinguish it from the application’s custom meter.

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Pull request overview

Documents existing .NET OpenTelemetry configuration and sensitive message-content controls without changing APIs or defaults.

Changes:

• Documents UseOpenTelemetry and EnableSensitiveData = false.
• Explains host-owned provider, source, and meter subscriptions.
• Clarifies content suppression versus event emission and distro limitations.

File summaries

File	Summary
dotnet/samples/02-agents/AgentOpenTelemetry/README.md	Adds telemetry configuration and sensitive-data guidance.

Review details

• Files reviewed: 1/1 changed files
• Comments generated: 1
• Review effort level: Lite (auto)

Note

Copilot is running an experiment and ran this review at Lite.

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