[joostlek]

Proposed change

Adds a single-new-integration check to the home-assistant/core manifest. It warns when a PR adds more than one new integration, which happens for example when someone adds several virtual integrations at once.

New integrations are detected by added homeassistant/components/<domain>/manifest.json files. A virtual integration only has a manifest.json and no __init__.py, so counting manifests catches those too. Manifests under tests/ are ignored.

• Two or more new integrations: warn, listing the domains and asking to split them into separate PRs, with a link to the review process.
• Exactly one: pass.
• None, or a release PR: skip.

It runs on opened, reopened, synchronize, and on-demand events, and is registered right after single-new-platform. The core manifest snapshots gain the new row.

Type of change

• Dependency upgrade
• Bugfix
• New rule or command
• New repository manifest (enable the bot on another repo)
• New feature (which adds functionality to an existing engine)
• Code quality improvement or refactor (incl. tests)

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:

Checklist

• I understand the code I am submitting and can explain how it works.
• The code change is tested and works locally.
• Local tests pass (mise run test). Your PR cannot be merged unless tests pass.
• Lint and type checks pass (mise run check).
• The code has been formatted (mise run format).
• Tests have been added to verify that the new code works.
• There is no commented out or debug code in this PR.
• Any generated code has been carefully reviewed for correctness and compliance with project standards.

If behaviour, configuration, or environment variables changed:

• README.md and .env.example have been updated accordingly.

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