Spool native cargo build and test streams to persistent world logs

PROTOCOL.md

@@ -448,9 +448,23 @@ builds `/plugins/notes/source/`:
 3. It builds the release `.wasm` for `wasm32-wasip2`. The tests and the build
    share the compiled dependencies.
 4. It returns `{"wasm": "/state/cargo/builds/<n>/notes.wasm", "tests":
-   {"passed", "failed", "output"}, "warnings"}`. If a step fails, it returns
+   {"passed", "failed", "output"}, "warnings", "logs"}`. If a step fails, it returns
    an error with the compiler or test output.
 
+- Before running commands, it creates `/logs/cargo/<YYYY-MM-DD>/<build-id>.stdout.log`
+  and `.stderr.log` (UTC date, unique build ID). Both test and release phases
+  append their raw bytes directly to these files, before any parsing, progress
+  filtering or UTF-8 conversion. This includes successful JSON build output.
+  `/logs` is a top-level world folder, created if missing, not under `/state`.
+- Success results and error -32004 `data` include `logs`:
+  `{"stdout":{"path":"/logs/cargo/...stdout.log","bytes":123},
+  "stderr":{"path":"/logs/cargo/...stderr.log","bytes":45},"total_bytes":168}`.
+  Counts are raw bytes, not characters. `logs` is null only if log creation
+  itself fails. Preparation failures otherwise include empty log files.
+  Inline diagnostics may be filtered or shortened; the files are the full truth.
+- Logs remain after failure, total/test timeout, and cancellation. Cancellation
+  need not return a result; its files remain discoverable in `/logs/cargo/`.
+  Pruning numeric `/state/cargo/builds/` artifact folders does not prune logs.
 - Optional `timeout_secs` is an integer of at least 1, default **900** (not
   null or unlimited). The wall-clock budget starts when the build acquires its
   mutex, excluding queue time, and covers tests and release compilation together.