docs: fix broken links in developer guides

[pratikgx]

Summary

Docs fix. Four relative links in the developer guides resolve to pages that don't exist. errorOnRelativeLinks is off in docs/astro.config.mjs, so the build doesn't catch them.

• development/Guides/creating-nodes.mdx (2 links): ../../../workflows/community-nodes resolves to /workflows/community-nodes. Now /features/workflows/community-nodes, the same form development/Architecture/invocations.mdx already uses.
• development/Setup/dev-environment.mdx: ../tests resolves to /development/setup/tests. Now /development/guides/tests.
• development/Guides/creating-node-pack.mdx: invocation-api.md has no matching page. Now /development/guides/api-development, which is where src/config/redirects.ts sends the old /nodes/invocation-api URL.

Root links get the base path added by rehypePrefixBaseToRootLinks, so they work on GitHub Pages too.

QA Instructions

Docs only. Each target page exists under docs/src/content/docs/.

Checklist

• The PR has a short but descriptive title, suitable for a changelog
• Tests added / updated (if applicable)
• ❗Changes to a redux slice have a corresponding migration
• Documentation added / updated (if applicable)
• Updated What's New copy (if doing a release after this PR)