fix(draupnir-slicer): warn that every invocation writes result.json to CWD

brokkr-smithy-dev exercised the slicer on real geometry and found OrcaSlicer
writes result.json into the working directory on --info. I verified it here and
it is worse: --help does it too, which is as read-only as an invocation gets.
An empty directory gained a result.json from --help alone.

Encoded in the wrapper and the Dockerfile rather than left to be rediscovered,
and the wrapper is now committed beside the image that backs it instead of
living only in a home directory on one host.

⚠ The reason they found it and I did not is worth keeping in the header: I
verified --help and called the slicer done. Usage text proves the binary
starts, not that it ingests our geometry or that it behaves while doing so.
They ran both controls through to STL and got manifold=yes, 520 facets,
return_code 0 on each -- which is the verification I should have run before
reporting the provisioning complete.

services/draupnir-slicer/Dockerfile

@@ -11,6 +11,11 @@
 # mean pinning permanently to a stale build — the exact trap brokkr-smithy-dev
 # rejected when choosing Orca over an old PrusaSlicer tag. A container keeps
 # the slicer current AND leaves the host untouched.
+# ⚠ RUNTIME TRAP, verified not inferred: OrcaSlicer writes result.json into the
+# WORKING DIRECTORY on every invocation — including --help, which is as
+# read-only as a call gets. An empty dir gained a result.json from --help alone.
+# Always invoke from inside the run's own artifact directory. The orca-slice
+# wrapper beside this file carries the same warning.
 FROM ubuntu:24.04
 ARG ORCA_VERSION=2.4.2
 ARG ORCA_URL=https://github.com/OrcaSlicer/OrcaSlicer/releases/download/v2.4.2/OrcaSlicer_Linux_AppImage_Ubuntu2404_V2.4.2.AppImage