docs(faststore-storefront): updates v3 to v4 migration reference

[hellofanny]

Description

• Adds Post-migration summary — mandatory structured output after completing all migration steps, including a per-file change table and a curated "Important next steps" section (WebOps Node.js v24, CMS content review, nested @import deprecation warnings).

• Adds CMS sync — step-by-step guidance for both Headless CMS (legacy yarn cms-sync) and Content Platform (generate-schema + upload-schema) paths, including the split-components / split-content-types pre-requisite for stores not yet in the new .jsonc format.

• Adds Safe deploy order — explicit 6-step sequence to avoid blank UI caused by deploying v4 before CMS fields are filled.

• Updates the review checklist to include CMS sync steps, local yarn dev verification, and the production deploy + WebOps Node.js v24 step.

• Fixes package.json snippet: removes next from dependencies (now managed internally by @faststore/cli) and adds graphql ^16.11.0 + note about typescript ^5.9.3 in devDependencies.

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Contribution Checklist

Before submitting, please verify:

• Source files only: Edited skill files in tracks/{track}/skills/{name}/skill.md, not in skills/, exports/, or rules/ directories
• Correct file name: Skill file is named skill.md (lowercase), not SKILL.md or other variants
• Frontmatter complete: Includes name, description, and metadata with track and tags fields
• Validation passed: Ran bun run validate and all hard checks pass
• Exports regenerated: Ran bun run export and committed both source and generated files
• Skill name format: Uses kebab-case and is unique across the repository
• Track directory correct: Track name in frontmatter matches the directory structure

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Public Documentation Sync

Public VTEX docs on developers.vtex.com and help.vtex.com may need to be updated when this PR ships. Pick one:

• No public docs change needed
• Public docs update required — list the affected pages and link the follow-up below:

See Public documentation sync in CONTRIBUTING.md for what triggers a docs update and how to find every affected page.

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Related Issues

[github-actions]

✅ Validation passed — all checks OK

Full validation output

$ bun run scripts/validate.ts --ci
Validating 45 skill files (9 hard, 4 soft checks)...

✅ tracks/payment/skills/payment-provider-framework/skill.md — 13/13 checks passed
✅ tracks/payment/skills/payment-pci-security/skill.md — 13/13 checks passed
✅ tracks/payment/skills/payment-async-flow/skill.md — 13/13 checks passed
✅ tracks/payment/skills/payment-provider-protocol/skill.md — 13/13 checks passed
✅ tracks/payment/skills/payment-idempotency/skill.md — 13/13 checks passed
✅ tracks/sales-app/skills/sales-app-extensibility/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-events-and-workers/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-render-runtime-and-blocks/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-service-configuration-apps/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-observability-and-ops/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-http-routes/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-data-access-patterns/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-app-settings/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-auth-tokens-and-context/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-rbac/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-app-contract/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-graphql-api/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-rootpath/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-storefront-theme-versioning/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-admin-react/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-masterdata/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-service-apps/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-security-boundaries/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-messages-and-i18n/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-react-apps/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-session-apps/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-service-runtime/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-storefront-react/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-service-paths-and-cdn/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-client-integration/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-application-performance/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-masterdata-strategy/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-storefront-theme-app/skill.md — 13/13 checks passed
✅ tracks/vtex-io/skills/vtex-io-auth-and-policies/skill.md — 13/13 checks passed
✅ tracks/architecture/skills/architecture-well-architected-commerce/skill.md — 13/13 checks passed
✅ tracks/marketplace/skills/marketplace-fulfillment/skill.md — 13/13 checks passed
✅ tracks/marketplace/skills/marketplace-catalog-sync/skill.md — 13/13 checks passed
✅ tracks/marketplace/skills/marketplace-rate-limiting/skill.md — 13/13 checks passed
✅ tracks/marketplace/skills/marketplace-order-hook/skill.md — 13/13 checks passed
⚠️  tracks/faststore/skills/faststore-storefront/skill.md — 10/13 checks passed (3 warnings)
   WARN: [required-sections] — Missing required H2 section: "## When this skill applies"
::warning file=tracks/faststore/skills/faststore-storefront/skill.md,title=required-sections::Missing required H2 section: "## When this skill applies"
   WARN: [required-sections] — Missing required H2 section: "## Decision rules"
::warning file=tracks/faststore/skills/faststore-storefront/skill.md,title=required-sections::Missing required H2 section: "## Decision rules"
   WARN: [required-sections] — Missing required H2 section: "## Hard constraints"
::warning file=tracks/faststore/skills/faststore-storefront/skill.md,title=required-sections::Missing required H2 section: "## Hard constraints"
   WARN: [required-sections] — Missing required H2 section: "## Preferred pattern"
::warning file=tracks/faststore/skills/faststore-storefront/skill.md,title=required-sections::Missing required H2 section: "## Preferred pattern"
   WARN: [required-sections] — Missing required H2 section: "## Common failure modes"
::warning file=tracks/faststore/skills/faststore-storefront/skill.md,title=required-sections::Missing required H2 section: "## Common failure modes"
   WARN: [required-sections] — Missing required H2 section: "## Review checklist"
::warning file=tracks/faststore/skills/faststore-storefront/skill.md,title=required-sections::Missing required H2 section: "## Review checklist"
   WARN: [detection-patterns] — No "Detection" or "**Detection**" pattern found in content
::warning file=tracks/faststore/skills/faststore-storefront/skill.md,title=detection-patterns::No "Detection" or "**Detection**" pattern found in content
   WARN: [paired-examples] — Missing correct example marker (✅ or **Correct**)
::warning file=tracks/faststore/skills/faststore-storefront/skill.md,title=paired-examples::Missing correct example marker (✅ or **Correct**)
   WARN: [paired-examples] — Missing incorrect example marker (❌ or **Wrong**)
::warning file=tracks/faststore/skills/faststore-storefront/skill.md,title=paired-examples::Missing incorrect example marker (❌ or **Wrong**)
✅ tracks/headless/skills/headless-caching-strategy/skill.md — 13/13 checks passed
✅ tracks/headless/skills/headless-checkout-proxy/skill.md — 13/13 checks passed
✅ tracks/headless/skills/headless-intelligent-search/skill.md — 13/13 checks passed
✅ tracks/headless/skills/headless-bff-architecture/skill.md — 13/13 checks passed
✅ tracks/masterdata/skills/masterdata-storage-strategy/skill.md — 13/13 checks passed

Summary: 44 passed, 1 warned (45 total)