Add integration test workflow for mngr

Adds a separate CI job that tests offload against a golden version of
the imbue-ai/mngr repository. The workflow:

1. Checks out both offload (current) and mngr (golden SHA)
2. Installs Rust, just, and uv for dependencies
3. Installs the current version of offload via `just install`
4. Installs mngr dependencies
5. Runs `just test-offload` in the mngr repo

Configuration:
- MNGR_SHA env var at top of file controls the golden version
- Requires MNGR_ACCESS_TOKEN secret for private repo access

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

Co-Authored-By: Claude <noreply@anthropic.com>
Co-authored-by: Sculptor <sculptor@imbue.com>

Author: 3 people

.github/workflows/integration.yml

@@ -0,0 +1,66 @@
+name: Integration
+
+on:
+  push:
+    branches: [ main ]
+  pull_request:
+    branches: [ main ]
+  workflow_dispatch:
+
+env:
+  CARGO_TERM_COLOR: always
+  # Golden version of mngr to test against
+  # Update this SHA when mngr changes in a way that affects offload integration
+  MNGR_SHA: "REPLACE_WITH_GOLDEN_SHA"
+
+jobs:
+  integration:
+    runs-on: ubuntu-latest
+
+    steps:
+    - name: Checkout offload
+      uses: actions/checkout@v4
+      with:
+        path: offload
+
+    - name: Checkout mngr (golden version)
+      uses: actions/checkout@v4
+      with:
+        repository: imbue-ai/mngr
+        ref: ${{ env.MNGR_SHA }}
+        token: ${{ secrets.MNGR_ACCESS_TOKEN }}
+        path: mngr
+
+    - name: Install Rust stable
+      uses: dtolnay/rust-toolchain@stable
+
+    - name: Install just
+      uses: taiki-e/install-action@v2
+      with:
+        tool: just
+
+    - name: Install uv (Python package manager)
+      uses: astral-sh/setup-uv@v4
+
+    - name: Cache Rust dependencies
+      uses: Swatinem/rust-cache@v2
+      with:
+        workspaces: offload
+
+    - name: Install offload (current version)
+      working-directory: offload
+      run: just install
+
+    - name: Install mngr dependencies
+      working-directory: mngr
+      run: |
+        if [ -f "requirements.txt" ]; then
+          uv pip install --system -r requirements.txt
+        fi
+        if [ -f "pyproject.toml" ]; then
+          uv pip install --system -e .
+        fi
+
+    - name: Run integration test
+      working-directory: mngr
+      run: just test-offload