chore: initial commit

Dockerfile

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+# Minimal dash-in-a-box for sekft trajectory generation.
+#   docker build -t sekft-dash .
+#
+# dash as the operated shell (strict POSIX, no bashisms), busybox applets for
+# the coreutils.  busybox is intentionally close to minimal POSIX so trajectories
+# transfer toward sek rather than encoding GNU-isms.  Add `coreutils findutils
+# grep sed` here if you want GNU semantics instead.
+FROM alpine:3.19
+RUN apk add --no-cache dash \
+ && ln -sf /usr/bin/dash /bin/dash \
+ && ln -sf /usr/bin/dash /bin/sh
+# /work is the default arena; provider files land at their absolute paths.
+RUN mkdir -p /work
+WORKDIR /work