Add three-axis milling with independent CAM and Fusion validation (#1682)

Thanks @CypherNaught-0x.

crates/doc/src/format/pending/manufacturing.rs

@@ -0,0 +1,4 @@
+//! Persistent milling setups, stock, fixtures, local tools, ordered operations, NC programs
+//! and durable profile/hole references. Older designs get empty manufacturing; explicit hole
+//! coordinates without references stay explicit. Generated paths and validation are not saved.
+//! Earlier released readers refuse the new format instead of discarding manufacturing.