nucleus-trace

The trace backend: decode pipeline + WebSocket fan-out.

Status (Phase 5 — complete)

OpenOCD (SWO) ──▶ source ──▶ Decoder ──▶ Translator ──▶ JSON ──▶ WebSocket :7878

• translate — pure, unit-tested meaning assignment: stimulus port 0 → reassembled UTF-8 log lines (replaces printf); ports 1–7 → typed values (f32/u16/u32/i32) named by [[trace.variables]]. Emits TraceEvents that serialize to JSON ({"kind":"log"|"variable"|"overflow", …}).
• server — TraceServer owns the decoder + translator, and broadcasts each event as JSON to every connected WebSocket client (tokio-tungstenite). A slow client drops messages rather than stalling the pipeline.
• source — SWO bytes from an OpenOCD TCP trace port (tpiu config internal :PORT …) or a captured-file replay, plus a best-effort OpenOCD telnet setup helper.
• run_blocking(TraceOptions) — the synchronous entry point nucleus trace calls.

An integration test (tests/websocket.rs) connects a real WebSocket client and asserts it receives the decoded log/variable JSON — the end-to-end Phase 5 exit criterion. Capturing from a physical NUCLEO-F446RE additionally requires OpenOCD + the ST-Link; the SWO command sequence is version-dependent (see source::openocd_enable).