Cover WooCommerce duplicate address semantics

[adamziel]

What it does

Adds focused WooCommerce HPOS plugin-validator coverage for duplicate address types on the same order. The test now models both branches independently adding a billing address for order 20 and verifies the merged state is held for review as plugin-woocommerce-hpos-duplicate-address-type.

Rationale

Generic SQLite merging can preserve all three rows because their IDs differ, but WooCommerce semantics expect one address per order_id + address_type. This is exactly the kind of plugin-owned invariant ForkPress needs validators to catch instead of auto-accepting as coherent.

Implementation

The WooCommerce HPOS test validator now groups wp_wc_order_addresses by order_id and address_type, skips missing-order cases already covered by existing checks, and emits a plugin conflict with structured logical identity:

{"plugin":"woocommerce","kind":"order_address_type","order_id":20,"address_type":"billing"}

The regression asserts the audit payload includes the base, source-created, and target-created address candidates.

Testing instructions

Ran locally after rebasing onto current origin/trunk:

php -l tests/cow/plugin_validator.php
make test-cow-plugin-validator
git diff --check

make test-cow-plugin-validator passed with 423 assertions.

[adamziel]

Rebased onto current trunk after #324. Local verification after rebase:\n\n- php -l tests/cow/plugin_validator.php\n- make test-cow-plugin-validator (423 assertions)