Probe a JSON-lines sidecar directly to split UI bugs from model bugs

When a UI feature backed by a stdio JSON-lines sidecar (here, a slang-based SystemVerilog design model used for waveform driver tracing) reports 'not a signal', pipe the same requests to the sidecar binary by hand on the host: printf the load request and then lookup/instance requests, one JSON object per line, into the binary. If the sidecar answers correctly (the instance has the array, and lookup of name[k] resolves), the bug is in the caller's path form. A common case is a waveform's memory-element name carrying a bit-range suffix like box[8][31:0], which an element regex anchored on ^name[k]$ rejects. Also check whether the sidecar's lookup returns ok for nonsense names; if it does, a 'does this exist' check built on it is not a real check.