Remove deprecated --shared-secret flag from shopify app webhook trigger

[alfonso-noriega]

WHY are these changes introduced?

The --shared-secret flag and SHOPIFY_FLAG_SHARED_SECRET environment variable on shopify app webhook trigger have been deprecated for some time in favor of --client-secret (SHOPIFY_FLAG_CLIENT_SECRET). The command currently renders a deprecation warning when --shared-secret is used and falls back to copying it into the service's clientSecret field. This PR removes the deprecated flag in preparation for the next major release.

Part of the deprecated-flag-removal stack: #7521 ← this PR → #7523.

WHAT is this pull request doing?

• Removes the --shared-secret flag definition and the SHOPIFY_FLAG_SHARED_SECRET env binding from shopify app webhook trigger.
• Removes the runtime deprecation warning.
• Removes the flags['client-secret'] || flags['shared-secret'] fallback in favor of just flags['client-secret'].
• Internal/service-level fields named sharedSecret (e.g. in the GraphQL request and send-app-uninstalled-webhook.ts) are intentionally untouched — they correspond to the GraphQL schema and are unrelated to the user-facing flag.
• Regenerates packages/cli/oclif.manifest.json, packages/cli/README.md, and docs-shopify.dev/commands/interfaces/app-webhook-trigger.interface.ts.

How to test your changes?

1. Run pnpm shopify app webhook trigger --shared-secret abc and confirm it now fails with an unknown-flag error.
2. Run pnpm shopify app webhook trigger --help and confirm --shared-secret is no longer listed and --client-secret is.
3. Run pnpm shopify app webhook trigger --client-secret <secret> ... end-to-end and confirm the webhook is signed and delivered as before.

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
• Remove deprecated --shared-secret flag from shopify app webhook trigger #7522 👈 (View in Graphite)
• Remove deprecated --force flag from shopify app release #7521
• Remove deprecated --force flag from shopify app deploy #7520
• main

This stack of pull requests is managed by Graphite. Learn more about stacking.

[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-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:webhook:trigger	--shared-secret
webhook:trigger	--shared-secret

🔧 Removed Environment Variables

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

Env Var	Previously Used By
SHOPIFY_FLAG_SHARED_SECRET	app:webhook:trigger --shared-secret, webhook:trigger --shared-secret