refactor(cli): drop cluster init — no replacement scaffold

Andrew's call, and the right one by the repo's own lens: a minimal
cluster.yaml is five lines; a generator is a second copy of the schema to
keep in sync forever, emitting a file that is unusable until hand-edited
anyway (graphs: {} cannot apply or serve). Terraform has no config
scaffolder either. New users copy from the cluster quick-start; migrants
get a ready-to-review cluster.yaml from config migrate. RFC-008 stage 3
becomes purely subtractive.

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

crates/omnigraph-cli/src/cli.rs

@@ -345,23 +345,6 @@ pub(crate) enum Command {
 
 #[derive(Debug, Subcommand)]
 pub(crate) enum ClusterCommand {
-    /// Scaffold a minimal cluster.yaml in the config directory (refuses
-    /// if one exists). The cluster checkout replaces the legacy
-    /// omnigraph.yaml scaffold (RFC-008 stage 3).
-    Init {
-        /// Directory to scaffold into (default: .)
-        #[arg(long, default_value = ".")]
-        config: PathBuf,
-        /// Optional deployment label (metadata.name)
-        #[arg(long)]
-        name: Option<String>,
-        /// Optional storage root URI (s3://bucket/prefix); omit for the
-        /// config-dir layout
-        #[arg(long)]
-        storage: Option<String>,
-        #[arg(long)]
-        json: bool,
-    },
     /// Validate cluster.yaml and referenced schemas, queries, and policy files.
     Validate {
         /// Cluster config directory containing cluster.yaml.