chore: move reference projects to their own repo (#3812)

The reference/example projects (`references/`) now live in their own
repo, https://github.com/triggerdotdev/references, so their heavy,
frequently-changing dependencies are no longer part of this repo's
lockfile and tooling. This removes them here and repoints everything
that referenced them.

- Deletes `references/`; updates the pnpm workspace + lockfile.
- Clears the references-only CI rules and `.vscode` configs.
- Repoints the docs (contributor/agent + one public page) to the new
repo.
- `seed.mts` keeps the local-dev projects (hello-world, d3-chat,
realtime-streams).

.github/workflows/check-review-md.yml

@@ -7,7 +7,6 @@ on:
       - "docs/**"
       - ".changeset/**"
       - ".server-changes/**"
-      - "references/**"
 
 concurrency:
   group: review-md-drift-${{ github.event.pull_request.number }}

.github/workflows/claude-md-audit.yml

@@ -8,7 +8,6 @@ on:
       - ".changeset/**"
       - ".server-changes/**"
       - "**/*.md"
-      - "references/**"
 
 concurrency:
   group: claude-md-audit-${{ github.event.pull_request.number }}

.github/workflows/pr_checks.yml

@@ -39,7 +39,6 @@ jobs:
               - '!.changeset/**'
               - '!hosting/**'
               - '!.github/**'
-              - '!references/**'
               - '!**/*.md'
               - '!**/.env.example'
       - uses: dorny/paths-filter@fbd0ab8f3e69293af611ebaee6363fc25e6d187d # v4.0.1