feat: add --template-version flag

[y-lakhdar]

Summary

Adds an optional --template-version <version> flag to @coveo/create-ui, allowing users to scaffold a specific version of a sample template instead of always resolving latest.

What it does

• Accepts an exact semver (e.g. 3.2.1) or an npm dist-tag (e.g. next, latest).
• Defaults to latest when omitted — existing behavior is unchanged.
• Validates the version against the package's published packument before extracting, and fails with a clear, actionable error if the version does not exist.

Usage

npm create @coveo/ui my-app --template headless-search-react --template-version 3.2.1

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Latest commit: 6339d08

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[Copilot]

Pull request overview

Adds support in @coveo/create-ui for pinning a scaffolded sample template to a specific published npm version or dist-tag via a new --template-version flag, while keeping the default behavior (latest) when omitted.

Changes:

• Added --template-version <version> CLI option, threaded through parsing → scaffolding → template download.
• Implemented packument-based validation for requested versions/dist-tags and a dedicated TemplateVersionUnavailableError.
• Updated docs/ADRs and tests to cover the new flag and behavior.

Reviewed changes

Copilot reviewed 9 out of 9 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
packages/create-ui/src/index.ts	Adds CLI flag parsing/help text, threads version into scaffold, and formats a version-aware “template unavailable” error.
packages/create-ui/src/index.test.ts	Adds unit tests for arg parsing, help text, version threading, and version-aware error messaging.
packages/create-ui/src/fs-utils.ts	Removes now-unused pathExists helper.
packages/create-ui/src/download.ts	Adds optional version support with packument validation and TemplateVersionUnavailableError.
packages/create-ui/src/download.test.ts	Adds tests for versioned extraction, dist-tag support, and rejection of unpublished versions.
packages/create-ui/README.md	Documents --template-version and explains how to pin sample versions.
packages/create-ui/docs/adr/002-sample-publishing.md	Updates ADR to reflect the new version pinning mechanism.
packages/create-ui/docs/adr/001-sample-consumption.md	Updates ADR to reflect default latest behavior plus optional version override.
.cspell.json	Adds “packument” to the dictionary.