more efficient CI

.github/actions/setup-build-env/action.yml

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+name: 'Setup Build Environment'
+description: 'Setup Go, install deps, cache/build FFI - everything needed to build'
+
+inputs:
+  go-version:
+    description: 'Go version to use'
+    required: true
+
+runs:
+  using: 'composite'
+  steps:
+    - name: Setup Go
+      uses: actions/setup-go@v5
+      with:
+        go-version: ${{ inputs.go-version }}
+        cache: true
+        cache-dependency-path: go.sum
+
+    - name: Install system dependencies (Ubuntu only)
+      run: |
+        if command -v apt-get &> /dev/null; then
+          sudo apt-get update
+          sudo apt-get install -y curl ca-certificates gnupg ocl-icd-opencl-dev libhwloc-dev
+        fi
+      shell: bash
+
+    - name: Download Go modules
+      run: go mod download
+      shell: bash
+
+    # Cache FFI build based on submodule commit
+    - name: Generate FFI cache key
+      id: ffi-cache-key
+      run: |
+        FFI_COMMIT=$(git -C extern/filecoin-ffi rev-parse HEAD 2>/dev/null || echo "unknown")
+        echo "key=ffi-${{ runner.os }}-${{ inputs.go-version }}-${FFI_COMMIT}" >> $GITHUB_OUTPUT
+      shell: bash
+
+    - name: Cache FFI build
+      id: cache-ffi
+      uses: actions/cache@v4
+      with:
+        path: |
+          extern/filecoin-ffi/.install-filcrypto
+          extern/filecoin-ffi/filcrypto.h
+          extern/filecoin-ffi/libfilcrypto.a
+          extern/filecoin-ffi/filcrypto.pc
+          build/.filecoin-install
+          build/.blst-install
+          extern/supraseal/.install-blst
+          extern/supraseal/deps/blst
+        key: ${{ steps.ffi-cache-key.outputs.key }}
+
+    - name: Build FFI
+      if: steps.cache-ffi.outputs.cache-hit != 'true'
+      run: make deps
+      shell: bash
+
+    - name: Restore FFI marker files
+      if: steps.cache-ffi.outputs.cache-hit == 'true'
+      run: |
+        mkdir -p build
+        touch build/.filecoin-install build/.blst-install || true
+      shell: bash

.github/images/build-env/Dockerfile

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+# Build environment for Curio CI
+# Contains: Go, system dependencies, and common tools
+# Rebuild when: Go version changes, system deps change, go.mod/go.sum change
+
+ARG GO_VERSION=1.24.7
+
+FROM golang:${GO_VERSION}-bookworm
+
+# Install system dependencies (same as install-deps action)
+RUN apt-get update && apt-get install -y \
+    curl \
+    ca-certificates \
+    gnupg \
+    ocl-icd-opencl-dev \
+    libhwloc-dev \
+    git \
+    && rm -rf /var/lib/apt/lists/*
+
+# Install Docker CLI (for test-itest to communicate with host Docker daemon)
+RUN install -m 0755 -d /etc/apt/keyrings && \
+    curl -fsSL https://download.docker.com/linux/debian/gpg -o /etc/apt/keyrings/docker.asc && \
+    chmod a+r /etc/apt/keyrings/docker.asc && \
+    echo "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/debian bookworm stable" > /etc/apt/sources.list.d/docker.list && \
+    apt-get update && \
+    apt-get install -y docker-ce-cli && \
+    rm -rf /var/lib/apt/lists/*
+
+# Set up workspace
+WORKDIR /workspace
+
+# Copy go.mod and go.sum to pre-download modules
+COPY go.mod go.sum ./
+
+# Pre-download Go modules (will be cached in /go/pkg/mod)
+RUN go mod download
+
+# Install common dev/CI tools (from tools/tools.go)
+RUN go install golang.org/x/tools/cmd/goimports@latest && \
+    go install github.com/hannahhoward/cbor-gen-for@latest && \
+    go install github.com/swaggo/swag/cmd/swag@latest
+

.github/workflows/build-env-image.yml

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+name: Build CI Environment Image
+
+on:
+  push:
+    branches: [main]
+    paths:
+      - '.github/images/build-env/**'
+      - '.github/workflows/build-env-image.yml'
+      - 'go.mod'
+      - 'go.sum'
+  workflow_dispatch:  # Allow manual trigger
+
+env:
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}/build-env
+
+jobs:
+  build-and-push:
+    runs-on: ubuntu-latest
+    permissions:
+      contents: read
+      packages: write
+
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Log in to Container Registry
+        uses: docker/login-action@v3
+        with:
+          registry: ${{ env.REGISTRY }}
+          username: ${{ github.actor }}
+          password: ${{ secrets.GITHUB_TOKEN }}
+
+      - name: Extract metadata
+        id: meta
+        uses: docker/metadata-action@v5
+        with:
+          images: ${{ env.REGISTRY }}/${{ env.IMAGE_NAME }}
+          tags: |
+            type=raw,value=latest
+            type=sha,prefix=
+
+      - name: Build and push
+        uses: docker/build-push-action@v5
+        with:
+          context: .
+          file: .github/images/build-env/Dockerfile
+          push: true
+          tags: ${{ steps.meta.outputs.tags }}
+          labels: ${{ steps.meta.outputs.labels }}
+