.NET: Update version for 1.19.0 release

[Roger Barreto (rogerbarreto)]

Motivation & Context

Bump the .NET version for the 1.19.0 release.

Description & Review Guide

• What are the major changes? Updates the version, Git tag, and date suffix.
• What is the impact of these changes? .NET packages will use version 1.19.0.
• What do you want reviewers to focus on? Confirm the release values.

Related Issue

N/A

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. If it is a breaking change, add the breaking change label (or add "[BREAKING]" to the title prefix, before or after any language prefix) — a workflow keeps the label and title prefix in sync automatically.

[Copilot]

Pull request overview

Updates the centralized .NET NuGet release metadata for version 1.19.0.

Changes:

• Bumps package and Git tag versions to 1.19.0.
• Updates the preview date suffix to 260822.

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[github-actions]

MAF Automated Review — Iteration 1

Result: No findings
Scope: full PR (1 commit(s)): 520621fb18a5
Model:gpt-5.6-sol

Overview

The PR consistently advances the central .NET package version and Git tag to 1.19.0 and updates preview builds to the 2026-08-22 date suffix. Existing project-level release flags continue to constrain GA, RC, and preview classification, while the repository's build workflow packs and installs representative artifacts. No Critical, High, or Medium defect introduced by this change was established.

Reviewed the supplied pull-request change set across correctness, security/reliability, architecture, and failure behavior.
No publishable findings remained after source verification for this scope.