docs: describe the deploy subtree

Rewrite the approval flow's step 4 as the three phases, with the reason
the rollback state is a git ref, and refresh the coordinator's node
inventory + dispatch table. Fix four doc comments that still pointed at
the deleted `run_merge_config_pr`.

hive-c0re/src/socket_server/config_approvals.rs

@@ -89,7 +89,7 @@ pub(super) fn handle_request_update_meta_inputs(
 /// dashboard shows the pending card immediately.
 ///
 /// The PR head sha is stored as `fetched_sha` on the approval row — the
-/// "reviewed sha" the approve handler (`run_merge_config_pr`) drift-gates
+/// "reviewed sha" the deploy's `MergeVerify` node drift-gates
 /// against before doing anything irreversible. This does NOT fetch the commit
 /// into the applied repo at submission time (that happens inside the approve
 /// handler, step 2, after the drift check). No flake pre-flight either —