Retires the workspace-global MethodNameCollision pre-pass
(crates/ailang-core/src/workspace.rs:547) via a phased three-iter
milestone. Iter 1 canonicalises InstanceDef.class, Constraint.class,
and SuperclassRef.class (extends ct.1's validator); Iter 2 installs
type-driven dispatch (method_to_candidate_classes index + multi-
candidate residual + AmbiguousMethodResolution / UnknownClass
diagnostics) while the workaround still gates real workspaces;
Iter 3 deletes the pre-pass and ships multi-class E2E plus DESIGN.md
sync. Unblocks the deferred milestone 24 (Show + print rewire).
Step 7.5 grounding-check PASS: all 18 load-bearing assumptions
ratified by named, currently-green tests.
