Name the runner environment each build step needs

Only a step's declared `required_environment` is forwarded to the runner
container. Odin's steps declared none, so CARGO_HOME and HOME never arrived
and cargo fell back to the image's read-only /usr/local/cargo, failing to
fetch the rev-pinned CultLib dependency.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

deployment/idunn/recipe.toml

@@ -7,12 +7,14 @@ required_gitlinks = []
 id = "test-odin-daemon"
 phase = "test"
 runner = "rust-build"
+required_environment = ["CARGO_HOME", "HOME"]
 argv = ["cargo", "test", "--locked", "-p", "odin-daemon"]
 
 [[steps]]
 id = "build-odin-daemon"
 phase = "build"
 runner = "rust-build"
+required_environment = ["CARGO_HOME", "HOME"]
 argv = [
   "cargo",
   "build",