fix(registry): update express docs_path after expressjs.com restructure

[moshest]

Summary

• The expressjs.com site migrated to Astro and moved English docs from /en to /src/content/docs/en, breaking the scheduled publish-all CI job with Directory not found: /tmp/context-git-…/en.
• Point docs_path at src/content/docs so the existing locale filter resolves the en/ subdirectory.

Test plan

• pnpm --filter @neuledge/registry registry build express — built 60 sections / 20,794 tokens locally.
• Scheduled publish-all workflow succeeds on next run.

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