fix: add jq to devcontainer image

[c-vigo]

Description

Install the Debian jq package in the vig-os devcontainer image so jobs that run inside ghcr.io/vig-os/devcontainer:<tag> can execute shell pipelines that pipe JSON through jq. This fixes downstream Release Core / Validate Release Core failures (exit 127 on Find and verify PR) when smoke-test (or any workspace) runs release-core.yml in-container; gh … --jq was never the problem—standalone jq was missing from the image.

Type of Change

• feat -- New feature
• fix -- Bug fix
• docs -- Documentation only
• chore -- Maintenance task (deps, config, etc.)
• refactor -- Code restructuring (no behavior change)
• test -- Adding or updating tests
• ci -- CI/CD pipeline changes
• build -- Build system or dependency changes
• revert -- Reverts a previous commit
• style -- Code style (formatting, whitespace)

Modifiers

• Breaking change (!) -- This change breaks backward compatibility

Changes Made

• Containerfile: add jq to the minimal apt-get install list (alphabetical with other packages).
• CHANGELOG.md: document under ## [0.3.1] - TBD → ### Added (sync-manifest also updates assets/workspace/.devcontainer/CHANGELOG.md).

Changelog Entry

This PR targets release/0.3.1; the entry lives under the active ## [0.3.1] - TBD section (not ## Unreleased).

- **`jq` in devcontainer image** ([#425](https://github.com/vig-os/devcontainer/issues/425))
  - Install the `jq` CLI in the GHCR image so containerized workflows (e.g. `release-core` validate / downstream Release Core) can pipe JSON through `jq`

Testing

• Tests pass locally (just test)
• Manual testing performed (describe below)

Manual Testing Details

N/A — image change only; optional verification: docker build -f Containerfile . then docker run --rm <image> jq --version.

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have commented my code, particularly in hard-to-understand areas
• I have updated the documentation accordingly (edit docs/templates/, then run just docs)
• I have updated CHANGELOG.md in the [Unreleased] section (and pasted the entry above)
• My changes generate no new warnings or errors
• I have added tests that prove my fix is effective or that my feature works
• New and existing unit tests pass locally with my changes
• Any dependent changes have been merged and published

Note: Changelog entry is under ## [0.3.1] - TBD → ### Added (release branch), not ## Unreleased, so the checklist item above is intentionally unchecked. No new tests for an OS package in the OCI image.

Additional Notes

• Failing job context: Release Core / Validate Release Core (exit 127 on Find and verify PR).
• After merge, a published image tag that includes this commit is required for downstream repos to pick up jq via .vig-os / DEVCONTAINER_VERSION.

Refs: #425