Add Dockerfile and GHCR publishing workflow

- Multi-stage Docker build for echidna binary
- GHCR workflow with artifact attestation
- SHA-pinned actions for security compliance

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: Jonathan D.A. Jewell

.github/workflows/ghcr-publish.yml

@@ -0,0 +1,65 @@
+# SPDX-License-Identifier: MIT OR Palimpsest-0.6
+name: Publish to GHCR
+
+permissions: read-all
+
+on:
+  release:
+    types: [published]
+  workflow_dispatch:
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+      id-token: write
+      attestations: write
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@b4ffde65f46336ab88eb53be808477a3936bae11 # v4
+
+      - name: Set up Docker Buildx
+        uses: docker/setup-buildx-action@c47758b77c9736f4b2ef4073d4d51994fabfe349 # v3
+
+      - name: Log in to GHCR
+        uses: docker/login-action@9780b0c442fbb1117ed29e0efdff1e18412f7567 # v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata
+        id: meta
+        uses: docker/metadata-action@369eb591f429131d6889c46b94e711f089e6ca96 # v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          tags: |
+            type=semver,pattern={{version}}
+            type=semver,pattern={{major}}.{{minor}}
+            type=ref,event=branch
+            type=sha
+
+      - name: Build and push
+        id: push
+        uses: docker/build-push-action@4f58ea79222b3b9dc2c8bbdd6debcef730109a75 # v6
+        with:
+          context: .
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+          cache-from: type=gha
+          cache-to: type=gha,mode=max
+
+      - name: Generate artifact attestation
+        uses: actions/attest-build-provenance@ef244123eb79f2f7a7e75d99086184180e6d0018 # v2
+        with:
+          subject-name: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          subject-digest: ${{ steps.push.outputs.digest }}
+          push-to-registry: true

Dockerfile

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+# SPDX-License-Identifier: MIT OR Palimpsest-0.6
+# SPDX-FileCopyrightText: 2025 ECHIDNA Project Contributors
+
+FROM rust:1.83-slim-bookworm AS builder
+
+WORKDIR /build
+
+RUN apt-get update && apt-get install -y \
+    pkg-config \
+    libssl-dev \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY Cargo.toml Cargo.lock* ./
+COPY src/ src/
+
+RUN cargo build --release
+
+FROM debian:bookworm-slim
+
+RUN apt-get update && apt-get install -y \
+    ca-certificates \
+    && rm -rf /var/lib/apt/lists/*
+
+COPY --from=builder /build/target/release/echidna /usr/local/bin/echidna
+
+ENTRYPOINT ["echidna"]
+CMD ["--help"]