IR-core unit tests

Per-crate, no I/O beyond synthetic inputs, parallel-safe. Live under crates/taktora-idl-core/tests/.

Test Case: Boundedness and structural-soundness contract TEST_0928
status: implemented
links incoming: REQ_0946, REQ_0947, REQ_0948

crates/taktora-idl-core/tests/boundedness.rs: constructs synthetic modules and asserts the boundedness contract — scalar wire sizes, integer-width narrowing, flat and nested struct sizing, bounded string and sequence bounds — and the structural checks — type / enum / field resolution, rejection of a recursive struct, rejection of duplicate names, and service request/response payload validation. Confirms validate and max_serialized_len behave per Boundedness is unrepresenta... (REQ_0946) and Structural validation befor... (REQ_0947), exercising the policy-free IR surface of Plane-generic, policy-free IR (REQ_0948).