[Maintenance] Fix invalid JSON schema syntax before validator reset

[ashleyshaw]

Maintenance / Chore Summary

Fix invalid JSON syntax in active schema files, especially JavaScript-style comments in project-fields.schema.json.

Parent epic: #285.

Steps / Checklist

• Identify schema files that fail strict JSON parsing.
• Remove comments or convert them to valid schema descriptions.
• Confirm schema files remain valid JSON.
• Documentation and changelog updated if needed.
• PR uses correct branch prefix maintenance/ or chore/.

Acceptance Criteria

• Active schema files parse as valid JSON.
• validate:json:schemas or replacement read-only check no longer fails on syntax.
• No schema meaning is lost without documentation.
• Approved by at least one maintainer.

[linear-code]

LS-626