Search Blocks: fix result and filter lists not rendering after results load

[lancewillett]

Related to FG-38

What

Fix the Search Blocks result list and filter buckets rendering empty after results load.

Why

Once @wordpress/interactivity is supplied by the host runtime (externalized from the build), the data-wp-each directive stops re-rendering a list when the bound array's reference is replaced after the initial render. The store replaced the arrays on every search (state.results = ( data.results ?? [] ).map( ... ), state.aggregations = remapAggregationsToFilterKeys( ... )).

At hydration state.results is the empty seeded array, so the each subscribes to that array instance and renders zero items. The fetch then assigns a brand-new array, so the each never re-renders — even though the store data, the result count, and scalar (data-wp-text / data-wp-bind) bindings all update correctly. Result: the results list and the filter buckets stay empty.

Fix

• Mutate the each-bound arrays/objects in place instead of reassigning, so the runtime keeps tracking the same container — results, aggregations, retainedFilterOptions, and loadMore's append (replaceStateArray / replaceStateObject). This is the load-bearing change.
• Declare those slots in the client store state so there is always a stable container.
• Correct the result/citation templates' data-wp-key → data-wp-each-key; data-wp-each reads its key from its own each-key directive, so data-wp-key on the <template> was a no-op.

Testing

• Added a store test asserting the each-bound containers keep their reference (in-place mutation) with updated contents after search(); all search-blocks JS tests pass (597).
• Verified end-to-end against a live page running the host Interactivity runtime that exhibits the bug: with the fix, the result list and filter facets render again (before: skeletons only / zero items; after: full results + facets).

🤖 Generated with Claude Code

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Code Coverage Summary

Coverage changed in 1 file.

File	Coverage	Δ%	Δ Uncovered
projects/packages/search/src/search-blocks/store/index.js	500/578 (86.51%)	0.24%	0 💚

Full summary · PHP report · JS report

[lancewillett]

@kangzj Requested review (this PR is AI-generated, so likely needs some more testing and validation). See FG-38 for the original report.

[lancewillett]

1216fc7 — Simplified the in-place helpers (removed unreachable type-guard branches, which closes the code-coverage gap CI flagged) and added 3 reference-stability tests: kept-key overwrite, stale-key drop, and loadMore in-place append. All assert toBe reference identity plus content. 600 search-blocks JS tests pass; eslint clean.