feat(devcontainers-cli): support pinned and mirrored installs

[Edd88-pixel]

Why

The module always installed the latest @devcontainers/cli release from the package manager's configured public source. That made reproducible installs and restricted-network workspaces difficult, while global installs could depend on elevated permissions.

Changes

• add validated inputs for an npm version or dist-tag and an optional npm-compatible registry URL
• install into Coder's agent-managed binary directory without sudo
• preserve existing package-manager detection and skip installation when devcontainer is already available
• propagate package-manager failures and verify the installed command is on PATH
• document pinned, mirrored, and air-gapped usage
• add Terraform tests, deterministic npm/pnpm/Yarn runtime coverage, and a real pinned npm installation test

Type of Change

• New module
• New template
• Bug fix
• Feature/enhancement
• Documentation
• Other

Module Information

Path: registry/coder/modules/devcontainers-cli
New version: v1.2.0
Breaking change: [ ] Yes [x] No

Validation

• terraform test — 4 passed
• bun test registry/coder/modules/devcontainers-cli/main.test.ts — 9 passed
• real npm installation of @devcontainers/cli@0.80.0 in node:22-alpine, followed by devcontainer --version
• terraform validate
• repository ShellCheck validation
• repository README validation
• targeted Prettier and Terraform formatting checks
• tsc --noEmit

Related Issues

Related to #427 and #308.

[Edd88-pixel]

@matifali could you review this please ?