feat: #3618698 Add the AI Translation Management (TMGMT) module to the recipe

Issue: #3618698 Add the AI Translation Management (TMGMT) module to the recipe

What changed

• composer.json: adds drupal/ai_tmgmt (~1) to the require block, after drupal/tmgmt, plus an AI translation keyword.
• README.md: documents the translation toolkit the recipe ships without enabling any of it — Translation Management Tool (drush en tmgmt tmgmt_content tmgmt_config tmgmt_local) and AI Translation Management (drush en ai_tmgmt, which needs an AI provider and model configured first). Also records that the core Translate tab reaches a Drupal Canvas page's title, URL alias, description and metatags only, so translating the copy inside components goes through a TMGMT job.
• CHANGELOG.md: the [Unreleased] entry.

Why

Varbase multilingual sites that want machine translation currently have to add the AI Translation Management Tool to their own project root. Shipping it in the recipe's require block puts it in the codebase, so a site can turn it on as a Translation Management Tool provider when it needs one.

Things a reviewer should know

• drupal/ai_tmgmt has no stable release. The newest tag is 1.0.0-beta6. The ~1 constraint resolves to it because Varbase project roots run minimum-stability: dev with prefer-stable: true. Verified with a real composer require --dry-run on a Varbase 11 project, which locked drupal/ai_tmgmt (1.0.0-beta6).
• It pulls the Drupal AI module in. At 1.0.0-beta6 the module requires drupal/ai ^1.0.4 and drupal/tmgmt ^1.16, so applying this recipe brings Drupal AI into the codebase even on sites that use no AI features.
• Nothing is enabled. The recipe does not enable ai_tmgmt; it does nothing until the site configures an AI provider and model. No API key is set by the recipe.

Testing

gitlab-ci-local run on this exact content, both jobs green:

• build:composer-validate — PASS
• validate:yaml-lint — PASS (0 YAML errors)

No functional install test of the new dependency has been run. Applying the recipe on a real Varbase 11 site with drupal/ai_tmgmt present has not been exercised, so the testing checkpoint below stays unticked.

AI-Generated: Yes

Checkpoints:

• File an issue
• Addition/Change/Update/Fix
• Testing to ensure no regression
• Automated unit testing coverage
• Automated functional testing coverage
• UX/UI designer responsibilities
• Readability
• Accessibility
• Performance
• Security
• Developer Documentation
• User Guide Documentation
• Reviewed by human
• Code review by maintainers
• Full testing and approval
• Credit contributors
• Review with the product owner
• Release notes snippet
• Release