CEXT-6421: fix starter kit links.

[obarcelonap]

Purpose of this pull request

After refactoring starter kits some links got broken, this PR attempts to fix them.
Please consider that some of the files has been rewritten in #578

Affected pages

• ...

Links to Magento Open Source code

• ...

[github-actions]

🔍 Linter Report

Click to expand full report

═══════════════════════════════════════════════════════════════
                     LINTER REPORT
═══════════════════════════════════════════════════════════════

Generated: 2026-07-21T14:57:32.258Z
Mode: Full Linting (all rules + dead links check)
Target Directory: /home/runner/work/commerce-extensibility/commerce-extensibility
Skipped Rules:
  - check-frontmatter → src/pages/_includes

───────────────────────────────────────────────────────────────

Files to process: 3

───────────────────────────────────────────────────────────────
📄 FILE: src/pages/app-development/app-submission-guidelines.md
───────────────────────────────────────────────────────────────
  ❌ ERROR
    Location: Line 56:122
    Message: Cannot find file `[https:/github.com/adobe/commerce-integration-starter-kit`. In EDS, a trailing slash (e.g., "./subdir/") resolves to "subdir/index.md", while no trailing slash (e.g., "./page") resolves to "page.md".
    Rule: missing-file

  ❌ ERROR
    Location: Line 56:122
    Message: Anchor link "[https://github.com/adobe/commerce-integration-starter-kit?tab=readme-ov-file#onboarding](https://github.com/adobe/commerce-checkout-starter-kit/blob/main/SUBMISSION_TEMPLATE.md#configure-eventing)" must include the .md file before the #anchor. Use "[https://github.com/adobe/commerce-integration-starter-kit/index.md#onboarding](https://github.com/adobe/commerce-checkout-starter-kit/blob/main/SUBMISSION_TEMPLATE.md" instead. Without .md, the sidenav will not work properly.
    Rule: anchor-link-extension

  ⚠️  WARNING
    Location: N/A
    Message: Invalid URL
    Rule: no-dead-urls


═══════════════════════════════════════════════════════════════
                        SUMMARY
═══════════════════════════════════════════════════════════════

  📁 Files processed:    3
  📄 Files with issues:  1
  ❌ Total errors:       2
  ⚠️  Total warnings:     1
  📋 Total issues:       3

Result: ❌ FAILED - Fatal errors found

═══════════════════════════════════════════════════════════════

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This comment was automatically generated by the linter bot.

[github-actions]

🔍 Linter Report

Click to expand full report

═══════════════════════════════════════════════════════════════
                     LINTER REPORT
═══════════════════════════════════════════════════════════════

Generated: 2026-07-21T15:43:50.361Z
Mode: Full Linting (all rules + dead links check)
Target Directory: /home/runner/work/commerce-extensibility/commerce-extensibility
Skipped Rules:
  - check-frontmatter → src/pages/_includes

───────────────────────────────────────────────────────────────

Files to process: 3

───────────────────────────────────────────────────────────────
📄 FILE: src/pages/app-development/app-submission-guidelines.md
───────────────────────────────────────────────────────────────
  ⚠️  WARNING
    Location: Line 57:47
    Message: Unexpected dead URL `https://github.com/adobe/commerce-integration-starter-kit?tab=readme-ov-file#onboarding`, expected live URL
    Rule: no-dead-urls


═══════════════════════════════════════════════════════════════
                        SUMMARY
═══════════════════════════════════════════════════════════════

  📁 Files processed:    3
  📄 Files with issues:  1
  ❌ Total errors:       0
  ⚠️  Total warnings:     1
  📋 Total issues:       1

Result: ⚠️  PASSED WITH WARNINGS - No fatal errors

═══════════════════════════════════════════════════════════════

---

This comment was automatically generated by the linter bot.