Python: Bump package versions for 1.19.0 release

[Evan Mattson (moonbox3)]

Motivation & Context

Prepare the next Python package release from the changes merged since python-1.18.0. This publishes generic vector-store capabilities, workflow and tool-loop enhancements, new MongoDB and Azure DocumentDB connectors, provider updates, and accumulated fixes across the independently versioned Python distributions.

Description & Review Guide

• What are the major changes? Adds the 1.19.0 CHANGELOG section; bumps 26 changed root-workspace distributions according to their lifecycle stages; updates the root package's exact Core pin; raises the Core dependency floor only for packages released in this cycle; and refreshes the root lockfile. Lab remains unchanged because its changes are development-only.
• What is the impact of these changes? Core and the root package move to 1.19.0; AG-UI moves to 1.4.0; Declarative moves to 1.1.0; Orchestrations moves to 1.2.0; Foundry and OpenAI receive patch releases; and changed alpha/beta packages receive the 260918 date stamp.
• What do you want reviewers to focus on? Confirm the CHANGELOG categorization and package coverage, the released-package semver decisions, the intentionally selective prerelease bumps, and the conservative Core floor updates.

Related Issue

N/A - scheduled Python release preparation.

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]

🟡 Changes recommended

The release is declared non-breaking despite confirmed breaking changes in stable packages, and two changelog entries misstate their linked changes.

Get a fresh assessment by requesting another Copilot review.

Pull request overview

Prepares the Python 1.19.0 release with coordinated package metadata and release notes.

Changes:

• Adds the 1.19.0 changelog.
• Bumps 26 distributions and applicable Core dependency floors.
• Applies incidental formatting updates to tests and annotations.

File summaries

File	Description
python/pyproject.toml	Bumps root package and Core pin.
python/packages/tools/pyproject.toml	Bumps Tools beta and Core floor.
python/packages/redis/pyproject.toml	Bumps Redis beta and Core floor.
python/packages/qdrant/pyproject.toml	Bumps Qdrant alpha and Core floor.
python/packages/purview/pyproject.toml	Bumps Purview beta and Core floor.
python/packages/orchestrations/tests/test_concurrent.py	Reformats an assertion.
python/packages/orchestrations/pyproject.toml	Bumps Orchestrations to 1.2.0.
python/packages/openai/pyproject.toml	Applies OpenAI patch release.
python/packages/monty/pyproject.toml	Bumps Monty beta and Core floor.
python/packages/mongodb/pyproject.toml	Bumps MongoDB alpha and Core floor.
python/packages/mistral/pyproject.toml	Bumps Mistral beta and Core floor.
python/packages/hyperlight/pyproject.toml	Bumps Hyperlight beta and Core floor.
python/packages/hosting-responses/pyproject.toml	Bumps Responses hosting alpha.
python/packages/hosting-mcp/pyproject.toml	Bumps MCP hosting alpha.
python/packages/hosting-a2a/pyproject.toml	Bumps A2A hosting alpha.
python/packages/foundry/pyproject.toml	Applies Foundry patch release.
python/packages/foundry_hosting/pyproject.toml	Bumps Foundry Hosting beta.
python/packages/devui/pyproject.toml	Bumps DevUI beta and Core floor.
python/packages/declarative/tests/test_graph_executors.py	Adjusts import spacing.
python/packages/declarative/pyproject.toml	Bumps Declarative to 1.1.0.
python/packages/core/tests/workflow/test_workflow.py	Adjusts class spacing.
python/packages/core/pyproject.toml	Bumps Core to 1.19.0.
python/packages/core/agent_framework/_workflows/_workflow.py	Normalizes union ordering.
python/packages/bedrock/pyproject.toml	Bumps Bedrock beta and Core floor.
python/packages/azure-documentdb/pyproject.toml	Bumps DocumentDB alpha.
python/packages/azure-cosmos/pyproject.toml	Bumps Cosmos beta and Core floor.
python/packages/azure-cosmos-memory/pyproject.toml	Bumps Cosmos Memory alpha.
python/packages/anthropic/pyproject.toml	Bumps Anthropic beta.
python/packages/ag-ui/tests/ag_ui/test_workflow_run.py	Reformats event collection.
python/packages/ag-ui/pyproject.toml	Bumps AG-UI to 1.4.0.
python/packages/a2a/pyproject.toml	Bumps A2A beta and Core floor.
python/CHANGELOG.md	Adds release notes and comparison links.

Review details

• Files reviewed: 32/33 changed files
• Comments generated: 3
• Review effort level: Balanced

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