Remove deprecated --type flag from shopify app generate extension

[alfonso-noriega]

WHY are these changes introduced?

The --type (-t) flag and SHOPIFY_FLAG_EXTENSION_TYPE environment variable on shopify app generate extension have been deprecated for some time in favor of --template (SHOPIFY_FLAG_EXTENSION_TEMPLATE). The command currently renders a deprecation warning and exits with code 2 when --type is used. This PR removes the deprecated flag in preparation for the next major release.

Part of the deprecated-flag-removal stack: #7522 ← this PR → #7524.

WHAT is this pull request doing?

• Removes the --type/-t flag definition and the SHOPIFY_FLAG_EXTENSION_TYPE env binding from shopify app generate extension.
• Removes the runtime deprecation warning and the process.exit(2) it triggered.
• Side-effect: the -t short alias now maps to --template. Previously both flags declared char: 't' and --type's registration shadowed --template, so -t effectively meant --type. After this change, -t consistently maps to --template.
• Regenerates packages/cli/oclif.manifest.json, packages/cli/README.md, and docs-shopify.dev/commands/interfaces/app-generate-extension.interface.ts.

How to test your changes?

1. Run pnpm shopify app generate extension --type ui-extension and confirm it now fails with an unknown-flag error.
2. Run pnpm shopify app generate extension --help and confirm --type is no longer listed.
3. Run pnpm shopify app generate extension --template <template> and confirm it works.
4. Run pnpm shopify app generate extension -t <template> and confirm -t now maps to --template (it would previously have mapped to --type and shown the deprecation warning).

Checklist

• I've considered possible cross-platform impacts (Mac, Linux, Windows)
• I've considered possible documentation changes
• I've considered analytics changes to measure impact
• The change is user-facing — I've identified the correct bump type (patch for bug fixes · minor for new features · major for breaking changes) and added a changeset with pnpm changeset add

[alfonso-noriega]

• Remove deprecated shopify theme serve command #7527
• Remove deprecated top-level shopify webhook trigger alias #7526
• Remove deprecated shopify app scaffold extension command #7525
• Remove deprecated shopify app generate schema command #7524
• Remove deprecated --type flag from shopify app generate extension #7523 👈 (View in Graphite)
• Remove deprecated --shared-secret flag from shopify app webhook trigger #7522
• Remove deprecated --force flag from shopify app release #7521
• Remove deprecated --force flag from shopify app deploy #7520
• main

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[github-actions]

⚠️ Potential Breaking Changes Detected

This PR contains changes that may break the existing contract.

@shopify/dev_experience — this PR contains breaking changes that require coordination for the next major release. This check will remain failed until a member of the team approves the workflow run.

💬 Head to #help-dev-platform to discuss timing and plan the release.

📦 Major Version Changesets

The following changesets request a major version bump:

Changeset	Package
remove-app-deploy-force-flag.md	'@shopify/app': major
remove-app-generate-extension-type-flag.md	'@shopify/app': major
remove-app-release-force-flag.md	'@shopify/app': major
remove-webhook-trigger-shared-secret-flag.md	'@shopify/app': major
thin-webs-notice.md	'@shopify/plugin-did-you-mean': major
thin-webs-notice.md	'@shopify/plugin-cloudflare': major
thin-webs-notice.md	'@shopify/create-app': major
thin-webs-notice.md	'@shopify/cli-kit': major
thin-webs-notice.md	'@shopify/store': major
thin-webs-notice.md	'@shopify/theme': major
thin-webs-notice.md	'@shopify/app': major
thin-webs-notice.md	'@shopify/cli': major
thin-webs-notice.md	'@shopify/e2e': major

🏳️ Removed Flags

The following flags were removed from existing commands:

Command	Flag
app:generate:extension	--type

🔧 Removed Environment Variables

The following env vars are no longer referenced in command flags:

Env Var	Previously Used By
SHOPIFY_FLAG_EXTENSION_TYPE	app:generate:extension --type