chore: add schema linter

[risu729]

No description provided.

[Copilot]

Pull Request Overview

This PR adds schema validation functionality to the project by introducing a new lint script that validates JSON schemas using AJV (Another JSON Schema Validator).

• Adds a new bash script for schema linting using AJV CLI
• Installs ajv-cli dependency for JSON schema validation
• Validates three schema files with different JSON Schema specifications

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
xtasks/lint/schema	New bash script that validates JSON schemas using AJV with different draft specifications
mise.toml	Adds npm:ajv-cli dependency for schema validation tooling

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[Copilot]

Inconsistent JSON Schema specification versions are being used. Lines 5-6 use draft2019 while line 7 uses draft2020. Consider standardizing on a single specification version unless there's a specific requirement for different versions.

Suggested change

	ajv compile -s schema/mise.plugin.json --spec=draft2020 --strict=true
	ajv compile -s schema/mise.plugin.json --spec=draft2019 --strict=true

[risu729]

This is intentional. It has:

  "$schema": "https://json-schema.org/draft/2020-12/schema",

[jdx]

nice! I had no idea we had so many issues!