Add unit json schema (infra)

[Hook25]

Description

This adds a json schema for yaml Checkbox units. This also adds pre-configuration for VS Code to simplify the life of those using it, which I think is why we committed it to the repo.

Minor: this fixes a missing exporter in the docs I found.

Resolved issues

Fixes: CHECKBOX-1396

Documentation

N/A

Tests

Tested locally with the vs code plugin + the neovim lsp plugin

[fernando79513]

This is very very cool.
I've run it in all the yaml files in the base provider, and mostly the linting issues were related to the estimated duration issues:
https://docs.google.com/spreadsheets/d/1G-8OoozIgTTThQCZA-tSOnv5Nyj1aDVDkQH5_vigtQY/edit?gid=0#gid=0

[fernando79513]

This field does not match the translated units.
The field is always translated as a string, but the linter looks for either a number or a specific pattern, so it fails validation:

id: audio/list_devices
estimated_duration: 1.0

id: audio/list_devices
estimated_duration: '1.0'

Raises this error.

Incorrect type. Expected "number".yaml-schema: Job Unit | Template Unit

We should either modify the translator so we do the parsing there so the new field in the yaml is estimated_duration: 1.0, or accept every string that matches a float in the linter estimated_duration: '1.0' probably going for the first one

We could even force the estimation parsing directly on the translation. Having both the float and the "h m s" approaches feels a bit weird to me. TBH, I don't think we are really using float estimations, but I think may be out of the scope for this PR.

[fernando79513]

There are several jobs that still use the "preserve-locale" flag, and it's marked as not existing.
We should remove this flag from all the jobs that use it in our repo, but especially from the docstrings in startprovider.py
BTW, its the first time I see the first try for Zygga to create a syntax highlighting:
https://github.com/canonical/checkbox/blob/main/checkbox-ng/contrib/pxu.vim

[fernando79513]

[GENERAL] We could also add "unevaluatedProperties": false,
That way, all the fields that are not evaluated will be marked by the linter:

unit: category
id: my_category
non-existing-field: field <- This will be linted

[fernando79513]

We are missing user-verify plugin

[fernando79513]

Do we know if we are really using these anywere?
I looked for many of them and couldn't find any usage in our codebase, I only see 5 of them in our exporter:

with-sys-info, with-summary, with-job-description, with-text-attachments,tp-export

[fernando79513]

[GENERAL] I think it's clearer if you add the name of the field to the title and have the unit in parenthesis like a subtitle, or if you preffer in the desciption:

```suggestion
    "unit": {
      "title": "Unit (Category Unit)",
      "description": "The type of unit.",
      "const": "category"
    },
    "id": {
      "title": "ID (Category Unit)",
      "description": "Unique identifier of the category.",
      "type": "string"
    },
    "name": {
      "title": "Name (Category Unit)",
      "description": "Human readable name of the category",
      "type": "string"
    }

[fernando79513]

This incidentally solves a weird issue, that after some investigation, I don't know why it's occurring. If you don't set the title per field, the unit title is inherited from the template schema

        "id": {
          "description": "Unique identifier of the job",
          "type": "string"
        },

But if you set the title section for each one of the unit fields, then the correct title appears:

        "id": {
          "title": "ID (Job Unit)",
          "description": "Unique identifier of the job",
          "type": "string"
        },

[Copilot]

Pull request overview

This PR introduces a JSON Schema set intended to validate Checkbox “unit” definitions (job/test plan/category/template/exporter/manifest entry/packaging meta-data), plus editor configuration to wire the schema into VS Code, and a small documentation correction for exporter units.

Changes:

• Added a top-level unit schema (unit.schema.json) and per-unit schemas under unit_json_schema/.
• Updated exporter documentation to include tar and tp-export as supported values/options.
• Added a VS Code YAML schema mapping to apply the unit schema to selected YAML file globs.

Reviewed changes

Copilot reviewed 10 out of 10 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
unit_json_schema/unit.schema.json	Entry-point schema that references the per-unit schemas via $ref.
unit_json_schema/job.schema.json	Schema for job units (shared fields + siblings).
unit_json_schema/test-plan.schema.json	Schema for test plan units including include/mandatory/bootstrapping fields.
unit_json_schema/category.schema.json	Schema for category units.
unit_json_schema/template.schema.json	Schema for template units (extends job fields).
unit_json_schema/exporter.schema.json	Schema for exporter units.
unit_json_schema/manifest-entry.schema.json	Schema for manifest entry units.
unit_json_schema/packaging-meta-data.schema.json	Schema for packaging meta-data units.
docs/reference/units/exporter.rst	Documentation update to reflect tar and tp-export.
.vscode/settings.json	VS Code YAML schema association configuration.

Key issues to address before this is practically usable in-repo (all verified against existing provider .pxu unit files and the docs in docs/reference/units/):

• All schemas use $id values pointing at a non-existent schema_checkbox/ path and also use GitHub blob/ URLs (HTML), which will break remote resolution and can break relative $ref resolution in some tooling.
• Several schemas require non-underscored fields (e.g. name, summary, template-summary) but existing units and docs consistently use translatable underscore forms (e.g. _name, _summary, _template-summary)—causing widespread validation failures.
• Multiple fields are typed as arrays in the schemas (e.g. depends, requires, imports, flags, environ), but are commonly expressed as scalar strings in existing .pxu units (and documented as space/comma-separated lists), which will also fail validation.
• template.schema.json restricts template-unit to const: "job", but the template unit documentation explicitly states other values may be used.
• .vscode/settings.json maps the schema to units/*.yaml globs, but this repository’s actual unit files are primarily providers/**/units/**/*.pxu (so the mapping won’t apply unless .pxu is associated and included).

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