feat(docker): opt-in gh + az CLIs with git credential helpers for private repos

Add Case -> Clone Repo could only reach public repositories in the Docker
deployment. This lets a deployment opt in to the GitHub CLI and the Azure
CLI (+ azure-devops extension) as git credential helpers. Codeman itself
still collects no credentials.

- server.Dockerfile / agent.Dockerfile: CODEMAN_INSTALL_GH /
  CODEMAN_INSTALL_AZ build args (0 or 1, default 0; anything else stops the
  build). Off leaves no apt repository, package, extension, helper script
  or credential entry, so a default build is unchanged. On installs from
  the vendors' apt repositories and configures system gitconfig helpers:
  github.com / gist.github.com -> `gh auth git-credential`, dev.azure.com /
  *.visualstudio.com -> new docker/git-credential-azure-cli (an Entra ID
  token from `az account get-access-token`, or AZURE_DEVOPS_EXT_PAT).
  A helper whose CLI is not signed in prints nothing, so a private clone
  still fails fast.
- The extension lives in AZURE_EXTENSION_DIR outside HOME
  (/opt/codeman-az-extensions, runtime-owned; /opt/az-extensions, gid-0
  group-writable in the agent image).
- Hosts turn them on in docker-compose.override.yml: `build: args:` for the
  server image, `environment:` CODEMAN_AGENT_IMAGE_INSTALL_GH / _AZ for the
  agent image. build-agent-image.mjs and the in-app auto-build share one
  env -> ARG table (pinned by the parity test) and pass nothing when unset.
  docker-compose.yaml is untouched; .env.example only gains a comment, so
  the self-updater's environment gate sees no new keys.
- Docker cases seed the gh sign-in (~/.config/gh/hosts.yml, config.yml) and
  the az sign-in files from ~/.azure per file, read-only, like pi/grok.
- The Clone Repo AUTH_REQUIRED message says how to sign the server's git
  in instead of claiming private repositories cannot be cloned.
- Docs: docker/README.md "Private repositories", docker-compose.md,
  docker-cases.md, the Quick-Start / Core-Concepts / Docker-Cases wiki
  pages, security-architecture.md, architecture-invariants.md, changeset.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_0167CiuzLrmjYWxwKp3rMWjw

docs/wiki/Docker-Cases.md

@@ -118,6 +118,32 @@ invisible from the host (`pi -c` and `grok -c` inside a docker case see only tha
 container's history). OMP's `sessions/` is the exception and is shared read-write, because
 Codeman reads it host-side for history and resume.
 
+**Git hosts.** The agent image can also include the GitHub CLI (`gh`) and the Azure CLI (`az`,
+with the `azure-devops` extension), off by default, and its git then uses them as credential
+helpers for github.com and Azure DevOps. Their sign-ins are seeded like everything else, file by file:
+`~/.config/gh/hosts.yml` and `config.yml`, and the sign-in files from `~/.azure` (not its
+logs or extensions). So once `gh auth login` / `az login` have been run where Codeman runs,
+agents in a Docker case can clone and push private repos on those hosts. Two limits:
+
+- A token held in a desktop keyring or an encrypted token cache (Windows, macOS) is not
+  inside those files and does not carry in. Sign in inside the container instead. The Docker
+  server image and a headless Linux host keep it in the files, so they carry.
+- The copy happens only when the file is not already in the container, so a sign-in made
+  after a case container was created reaches that container only once it is recreated
+  (or once you sign in inside it).
+
+This hands a GitHub token and an Azure sign-in to every agent in a seeded Docker case, the
+same trust you already give it with Claude, Codex or gcloud. Turn seeding off for a case that
+should not have them.
+
+Both CLIs are opt-in. To build the agent image with them, set
+`CODEMAN_AGENT_IMAGE_INSTALL_GH=1` and/or `CODEMAN_AGENT_IMAGE_INSTALL_AZ=1` where the image
+is built: in front of `node scripts/build-agent-image.mjs`, or in the Codeman server's
+environment for the image it builds automatically (in the Docker deployment, `environment:`
+in `docker-compose.override.yml`), then rebuild the image with `--no-cache`.
+`docker/README.md` ("Private repositories") has the details and the matching switches for
+the server image.
+
 ## Isolation
 
 Every container runs hardened by default: