fix: resolve product variation type when the node is a base Post model

[kidunot89]

Summary

Post_Types::resolve_product_variation_type() assumes $value is a Product_Variation model and calls $value->get_type(). When a variation node is loaded through the generic post loader instead — e.g. a cart item's variation.node on a site running Polylang, which doesn't manage the product_variation post-type — $value arrives as a base \WPGraphQL\Model\Post with no get_type(), and the resolver fatals (surfacing downstream as "Callback returned incorrect type; expected Promise").

This adds a fallback: when get_type() isn't callable, resolve the variation's product type from its ID via wc_get_product(). The error message also reports the resolved $product_type instead of the now-possibly-absent $value->type.

Also removes a stray graphql_debug() left in the ProductWithPricing price resolver.

Test plan

• Query a cart whose items have variations on a Polylang-enabled store (cart.contents.nodes[].variation.node) — previously fataled, now resolves the correct ProductVariation type.
• Query a variation through the normal Product_Variation model path — unchanged (still uses get_type()).
• Query a variation of an unsupported product type — still throws the "not supported" UserError (now with the resolved type name).

[coveralls]

Coverage Report for CI Build 28297639419

Coverage increased (+0.001%) to 91.801%

Details

• Coverage increased (+0.001%) from the base build.
• Patch coverage: 1 uncovered change across 1 file (6 of 7 lines covered, 85.71%).
• No coverage regressions found.

Uncovered Changes

File	Changed	Covered	%
includes/class-post-types.php	7	6	85.71%

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	20186
Covered Lines:	18531
Line Coverage:	91.8%
Coverage Strength:	153.15 hits per line

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💛 - Coveralls