Codegen tests

Test cases for the codegen crate (Network-config codegen (FEAT_0082)). Per-crate, snapshot-based. Live under crates/ethercat-netcfg-codegen/tests/.

Test Case: Generated module emits the expected static PDO_MAP TEST_0834
status: open
verifies: REQ_0825

Golden-file test: codegen over the WAGO fixture produces a pub static PDO_MAP: &[SubDeviceMap] whose single entry carries the computed address, the mapped PdoEntry slices, and the derived expected_wkc. Snapshot compared against a checked-in golden module.
Test Case: Generated routing and channel-name constants match the bindings TEST_0835
status: open
verifies: REQ_0826

For each channel binding in the fixture, the generated module exposes a named EthercatRouting constant carrying the resolved subdevice address, direction, bit offset, and bit length, plus the channel-name string constant. Asserted against the golden snapshot.
Test Case: Configured addresses follow bus position, override honoured TEST_0836
status: open
verifies: REQ_0827

A three-device fixture generates addresses 0x1000, 0x1001, 0x1002 in list order. A second fixture with an explicit address: 0x1005 override on the middle device generates 0x1000, 0x1005, 0x1002. Confirms positional assignment and the escape hatch of Positional addressing; alia... (ADR_0093).
Test Case: expected_wkc is derived from PDO directions TEST_0837
status: open
verifies: REQ_0828

Property test over fixtures: a TxPDO-only device generates expected_wkc = 2, an RxPDO-only device 1, a both-directions device 3, and a PDO-less coupler 0 — the canonical 0/1/2/3 rule. No fixture is able to express an override value; the schema carries no such field (guards Working-counter expectation... (ADR_0095)).
Test Case: Generated output is byte-deterministic TEST_0838
status: open
verifies: REQ_0829

Codegen runs twice over the same fixture and pinned ESI inputs; the two emitted modules are byte-identical. A variant reorders unrelated YAML keys and confirms the output is unchanged. No timestamp or hash-map iteration order leaks into the file.