Add support for µg/m³ unit of measurment device class Carbon Monoxide

[wittypluck]

Proposed change

Add support for µg/m³ unit of measurment device class Carbon Monoxide

Type of change

• Document existing features within Home Assistant
• Document new or changing features for which there is an existing pull request elsewhere
• Spelling or grammatical corrections, or rewording for improved clarity
• Changes to the backend of this documentation
• Remove stale or deprecated documentation

Checklist

• I have read and followed the documentation guidelines.
• I have verified that my changes render correctly in the documentation.

Additional information

• This PR fixes or closes issue: fixes #
• Link to relevant existing code or pull request: Add support for μg/m³ for Carbon Monoxide core#153158

Summary by CodeRabbit

• Documentation
  • Updated CO device class unit listings to include µg/m³ alongside ppm and mg/m³, improving clarity on supported measurement units.
  • Synchronized the Available device classes tables across relevant pages to ensure consistent guidance.
  • No functional, API, or behavior changes; this is a documentation-only update aimed at better unit awareness for users configuring sensors and entities.

[coderabbitai]

📝 Walkthrough

Walkthrough

Documentation updates adding "µg/m³" as an additional unit for carbon monoxide (CO) in number and sensor device class tables. No code, behavior, API, or control-flow changes.

Changes

Cohort / File(s)	Summary of Changes
Docs: CO unit additions docs/core/entity/number.md, docs/core/entity/sensor.md	Expanded CO device class unit lists to include "µg/m³" alongside existing "ppm, mg/m³".

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Pre-merge checks and finishing touches

✅ Passed checks (3 passed)

Check name	Status	Explanation
Title Check	✅ Passed	The title accurately summarizes the primary change by stating that support for the µg/m³ unit is being added to the Carbon Monoxide device class, making it clear and focused on the main documentation update. It is concise and specific, helping teammates quickly understand the purpose of the pull request. However, there is a typo in the word “measurement” that should be corrected.
Description Check	✅ Passed	The pull request description follows the repository’s template by including the required sections: a clear proposed change, a single type-of-change checkbox selected, a completed checklist, and additional information with a link to the related core pull request. All mandatory headings and template comments are preserved, providing sufficient context for reviewers. The only minor ambiguity is the placeholder “fixes #” which could be clarified or removed if no issue is being closed.
Docstring Coverage	✅ Passed	No functions found in the changes. Docstring coverage check skipped.

✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment

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📜 Recent review details

Configuration used: CodeRabbit UI

Review profile: CHILL

Plan: Pro

Cache: Disabled due to data retention organization setting

Knowledge base: Disabled due to data retention organization setting

📥 Commits

Reviewing files that changed from the base of the PR and between 4180e26 and 925d4b1.

📒 Files selected for processing (2)

• docs/core/entity/number.md (1 hunks)
• docs/core/entity/sensor.md (1 hunks)

🚧 Files skipped from review as they are similar to previous changes (2)

• docs/core/entity/sensor.md
• docs/core/entity/number.md

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