Fix Test Failure - TestScanAsync_InvalidCursorId

[currantw]

Problem

The TestScanAsync_InvalidCursorId test was failing due to a race condition in the Rust FFI layer. When an invalid cursor ID was provided to cluster scan operations, the Rust code was calling the failure callback twice:

1. First callback: Immediate failure when detecting invalid cursor ID.
2. Second callback: From the panic guard when the function exited, because panic_guard.panicked was not set.

This caused SetException to be called multiple times on the same Message object in C#, leading to assertion failures and process crashes. This caused the test runner to stall while it waited for the process to complete.

Solution

1. Fixed double callback issue: Added panic_guard.panicked = false before early returns to prevent the panic guard from triggering additional failure callbacks
2. Improved error handling: Used report_error function instead of manual string formatting to avoid potential dangling pointer issues
3. Simplified test: Refactored the test to use inline lambda expressions for cleaner code

Changes

• rust/src/lib.rs: Fixed panic guard handling and improved error reporting in request_cluster_scan
• tests/Valkey.Glide.IntegrationTests/ScanTests.cs: Simplified test implementation

Fixes #132

[Copilot]

Pull Request Overview

This PR refactors error handling in the cluster scan functionality and simplifies the corresponding test. The changes improve code consistency and fix potential panic reporting issues.

• Refactored Rust error handling to use the report_error helper function consistently
• Added proper panic guard cleanup before early returns to prevent false panic reporting
• Simplified C# test code by removing unnecessary intermediate variables

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
tests/Valkey.Glide.IntegrationTests/ScanTests.cs	Simplified test by inlining client creation and removing unused exception variable
rust/src/lib.rs	Fixed error reporting to use helper function and properly reset panic guard before early returns

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[yipin-chen]

LGTM