Fixing RPCs broken by dropping json-rpc support

This fixes the raw-ish reconcile RPC by replacing the JSON-RPC call with the supported alternative, HttpBatch.

Also fixed:
- image preview: we were asking for an image of size 5000 when the max is 4096.
- output.ts: pred/sub vs. p/s. No idea why this wasn't working, or if this is the right thing, but it doesn't throw an error now.