🧪 [Testing Improvement] Add Out-Of-Memory test for HashMap resize logic

[void0x14]

🎯 What: The testing gap addressed is the missing coverage for the Out-Of-Memory (OOM) handling branch within HashMap.resize().
📊 Coverage: This patch introduces a robust test case covering the exact scenario where the try self.allocator.alloc fails when the HashMap naturally reaches its threshold and attempts to double its capacity. It uses std.testing.FailingAllocator with .fail_index = 1 to successfully initialize the struct but simulate allocation failure strictly during the resize function called inside put. It checks that error.OutOfMemory is accurately returned and asserts the integrity of all pre-existing elements.
✨ Result: The test suite now guarantees data preservation during internal allocation failures on resizing. Code coverage in echo-core-zig/src/data/hashmap.zig is improved and ensures no items are corrupted when reaching memory limits.

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PR created automatically by Jules for task 124247147783657865 started by @ulac000000

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