Supply SSH key for channel config repo access (#9298)

.github/actions/prepare_environment/action.yml

@@ -15,6 +15,8 @@ inputs:
     description: If true, dependencies needed for building release artifacts will be installed (e.g., cargo-about for license generation).
   cache_key:
     description: If set, the cache key to use.  If unset, the cache key will be derived from the target OS.
+  ssh_key:
+    description: SSH private key used to clone the private warp-channel-config repository. Only consumed when running in warpdotdev/warp-internal.
 
 runs:
   using: composite
@@ -74,6 +76,15 @@ runs:
       env:
         BINSTALL_VERSION: 1.14.4
 
+    # Load the SSH key needed to clone the private warp-channel-config repo. Only
+    # run in warpdotdev/warp-internal; elsewhere (mirrors, fork PRs) this is a no-op
+    # and install_channel_config falls back gracefully.
+    - name: Setup SSH keys for warp-channel-config
+      if: ${{ github.repository == 'warpdotdev/warp-internal' && inputs.ssh_key != '' }}
+      uses: webfactory/ssh-agent@e83874834305fe9a4a2997156cb26c5de65a8555 # v0.10.0
+      with:
+        ssh-private-key: ${{ inputs.ssh_key }}
+
     - name: Install dependencies
       shell: bash
       run: |