Support workflow variable binding for the Send Email action's Attachments field

Scope & Context We use the Send Email workflow action for stage-change emails and need to attach a document that lives on the triggering record (e.g. a contract file stored on an Opportunity), so each email carries that record's own file. This ticket covers the Send Email node's Attachments field only. Current behavior In the Send Email workflow action, the Attachments field (WorkflowSendEmailAttachments) only allows static file uploads. It has no VariablePicker, unlike the To / Subject / Body fields in the same node, which already accept workflow variables. So the same fixed file is attached on every run; you cannot attach a file that lives on the triggering record. [screenshot of the Attachments field with no variable option] Expected behavior The Attachments field should accept a workflow variable (e.g. a record Files field), alongside static uploads, so the per-record file(s) are attached at runtime. Note: the backend already supports this end to end, only the…