workflowType reports "read" for newly created write-only workflows

## What

`deriveWorkflowType(nodes, requestedType)` (`lib/mcp/calldata.ts`) correctly classifies a workflow as `read`/`write` from its node actionTypes, and is already called from both places that update a workflow's `workflowType` (the PATCH handler and `lib/mcp/listing.ts`'s publish/patch paths) — but it is never called from `POST /api/workflows/create`. The `workflows.workflowType` column defaults to `"read"` (NOT NULL), so every newly created workflow reports `"read"` regardless of its actual nodes, until a later PATCH happens to correct it.

## How I ran into it

Found during the hackathon while inspecting a workflow I'd just created via `POST /api/workflows/create` with a single `web3/write-contract` node — the response reported `workflowType: "read"` despite the workflow having no read step at all.

Fix proposed in #2011.

Start at the POST /api/workflows/create handler and read deriveWorkflowType in lib/mcp/calldata.ts, then compare the existing PATCH and lib/mcp/listing.ts publish/patch paths. Ensure creation derives workflowType from the submitted nodes so a write-only workflow is returned as write rather than the database default read.

Written by the indexing model from the issue text.