Fix flaky mcp_server tests with Python 3.14.3

[epenet]

Proposed change

Alternative to #169385

Spotted in https://github.com/home-assistant/core/actions/runs/25057100718/job/73402201810?pr=162263

Needed for #162263

Under some circumstances, it seems that conversation can be loaded before homeassistant component has finished loading.

2026-04-28 14:14:38.268 INFO     SyncWorker_0 homeassistant.loader:loader.py:785 Loaded mcp_server from homeassistant.components.mcp_server
2026-04-28 14:14:38.270 INFO     SyncWorker_0 homeassistant.loader:loader.py:785 Loaded homeassistant from homeassistant.components.homeassistant
2026-04-28 14:14:38.271 INFO     SyncWorker_0 homeassistant.loader:loader.py:785 Loaded http from homeassistant.components.http
2026-04-28 14:14:38.272 INFO     MainThread homeassistant.setup:setup.py:393 Setting up http
2026-04-28 14:14:38.276 INFO     SyncWorker_0 homeassistant.loader:loader.py:785 Loaded conversation from homeassistant.components.conversation
2026-04-28 14:14:38.280 INFO     SyncWorker_0 homeassistant.loader:loader.py:785 Loaded intent from homeassistant.components.intent
2026-04-28 14:14:38.281 INFO     MainThread homeassistant.setup:setup.py:393 Setting up intent
2026-04-28 14:14:38.283 INFO     MainThread homeassistant.setup:setup.py:393 Setting up conversation
2026-04-28 14:14:38.284 ERROR    MainThread homeassistant.setup:setup.py:438 Error during setup of component conversation: 'homeassistant.exposed_entities'
2026-04-28 14:14:38.286 INFO     MainThread homeassistant.setup:setup.py:393 Setting up homeassistant

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
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• Breaking change (fix/feature causing existing functionality to break)
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• This PR fixes or closes issue: fixes #
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[home-assistant]

Hey there @allenporter, mind taking a look at this pull request as it has been labeled with an integration (mcp_server) you are listed as a code owner for? Thanks!

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[Copilot]

Pull request overview

This PR addresses flaky mcp_server test failures under Python 3.14.3 by ensuring the core homeassistant component is set up for all tests in the tests/components/mcp_server package.

Changes:

• Add an autouse pytest fixture to set up the homeassistant component before tests run.

[epenet]

In production, "homeassistant" is always loaded first. It doesn't not need to be present in dependencies so I have removed it.

core/homeassistant/bootstrap.py

Line 147 in f3acae6

CORE_INTEGRATIONS = {"homeassistant", "persistent_notification"}

[jbouwh]

LGTM,
Thanks @epenet 👍