feat: support multi-value array properties for non-set operators

[kyeh-amp]

Summary

Non-set operators (is, contains, greater, etc.) previously coerced array/list properties to a single JSON-stringified value, diverging from analytics/charts behavior where any element of an array can satisfy the condition.

• matchCondition now consults coerceStringList for every non-null value and dispatches to a new matchStringsNonSet helper when the value coerces to a list — any-match semantics, including for negation operators (is not, does not contain), which match if any single element satisfies the negation.
• coerceStringList gains a strings.HasPrefix(s, "[") pre-check so scalar strings skip JSON parsing now that every value passes through it.
• User-visible consequence: JSON-array strings with leading whitespace (e.g., " [\"a\"]") are no longer parsed as arrays by set operators.

Test plan

• Inline flag/condition harness drives 14 evaluation-engine unit cases (scalar / collection / JSON-array-string × set and non-set operators)
• 7 integration tests against the superset deployment (server-VVhLULXCxxY0xqmszXouXxiEzoeJWmSh)
• Pre-existing evaluation tests unchanged (segment-name assertions still match the superset deployment)
• go vet ./... clean
• go test ./internal/evaluation/... passes

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Note

Medium Risk
Changes core flag condition matching semantics so non-set operators (is, contains, comparisons, regex) can match any element of an array/JSON-array-string, which could change targeting results for existing flags. Also tightens JSON-array-string detection (HasPrefix("[")), which may stop parsing arrays with leading whitespace for set operators.

Overview
Updates matchCondition so non-set operators evaluate array-like properties (slices/arrays or JSON-array-strings) using any-element semantics via new matchStringsNonSet, instead of coercing the whole value to a single string.

Adds a fast HasPrefix("[") guard in coerceStringList to avoid unnecessary JSON parsing now that list coercion runs for all non-null properties, and expands tests with both remote integration cases and an inline flag/condition harness to cover scalar vs multi-value behavior (including negation and whitespace edge cases).

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[github-actions]

🎉 This PR is included in version 1.11.0 🎉

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