Update docs/usage.md

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: lpcox

docs/usage.md

@@ -37,10 +37,11 @@ Options:
   --image-registry <registry>  Container image registry (default: ghcr.io/github/gh-aw-firewall)
   --image-tag <tag>            Container image tag (default: latest)
                                Optional digest metadata:
-                                 <tag>,squid=sha256:...,agent=sha256:...,api-proxy=sha256:...
-                                Image name varies by --agent-image preset:
-                                  default → agent:<tag>
-                                  act     → agent-act:<tag>
+                                 <tag>,squid=sha256:...,agent=sha256:...,agent-act=sha256:...,api-proxy=sha256:...,cli-proxy=sha256:...
+                                 Supported digest metadata keys: squid, agent, agent-act, api-proxy, cli-proxy
+                                 Image name varies by --agent-image preset:
+                                   default → agent:<tag>
+                                   act     → agent-act:<tag>
   --skip-pull                  Use local images without pulling from registry (requires images to be
                                pre-downloaded) (default: false)
   -e, --env <KEY=VALUE>        Additional environment variables to pass to container (can be