Gitea Act Runner: DinD stack with cache + parallel jobs

Stable docker-compose setup for building Rust projects on Gitea Actions.
DinD-isolated daemon, built-in cache server, capacity=4 parallel jobs,
healthcheck-gated startup. Portable to other build machines via .env.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HU4wDwdydNZpR3YkMiYYy8

config.yaml

@@ -0,0 +1,44 @@
+log:
+  level: info
+
+runner:
+  # Run multiple jobs concurrently. Overridden by env at compose level too.
+  capacity: 4
+  timeout: 3h
+  # Keep the runner alive; jobs are ephemeral containers.
+  insecure: false
+  # Env injected into every job. Speeds up Rust builds.
+  envs:
+    CARGO_TERM_COLOR: always
+    CARGO_INCREMENTAL: "0"
+    CARGO_NET_RETRY: "10"
+  fetch_timeout: 5s
+  fetch_interval: 2s
+  # Labels decide which docker image runs each job. Jobs use `runs-on: ubuntu-latest`.
+  labels:
+    - "ubuntu-latest:docker://catthehacker/ubuntu:act-22.04"
+    - "ubuntu-22.04:docker://catthehacker/ubuntu:act-22.04"
+    - "ubuntu-24.04:docker://catthehacker/ubuntu:act-24.04"
+
+cache:
+  # Built-in cache server so actions/cache works (Rust deps, target/, etc.)
+  enabled: true
+  dir: ""
+  # Empty host -> auto-detect outbound IP reachable from job containers.
+  host: ""
+  port: 0
+
+container:
+  # Talk to the DinD daemon, not the host.
+  network: ""
+  privileged: false
+  options: ""
+  workdir_parent: ""
+  # Allow workflows to mount caches from the DinD volume.
+  valid_volumes:
+    - "**"
+  docker_host: "-"
+  force_pull: false
+
+host:
+  workdir_parent: ""