Add SDK health check method with RPC connectivity report

[Kingsman-99]

Overview

There is no way for an app to verify that the SDK can reach the configured RPC endpoint before making real calls. Add a healthCheck() method that probes connectivity and returns a diagnostic report.

Acceptance Criteria

• sdk.healthCheck() returns Promise<HealthCheckResult>
• HealthCheckResult: { rpcReachable: boolean, latencyMs: number, network: string, contractDeployed: boolean, error?: string }
• rpcReachable: whether the RPC endpoint responded to a getLatestLedger call
• latencyMs: round-trip time for the probe call
• contractDeployed: whether get_contract_data returns a result for the configured contract ID
• error: human-readable message if any check failed
• healthCheck() has a 5-second timeout; times out with HealthCheckTimeoutError
• Useful for app startup checks and connection debugging
• Does not throw on failure — returns the result object with rpcReachable: false

[uzochukwuV]

@uzochukwuV has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I'd love to work on this issue

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[BigElv]

@BigElv has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hi maintainer I would love to work on this issue please

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[Malcolm-Wander]

@Malcolm-Wander has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hello maintainer,I’d love to work on this issue please…promise to do bad accurate and swift job,thank you.

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[opeolarewaju5-glitch]

@opeolarewaju5-glitch has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

Hello Maintainer, I can fix this issue.

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[wowamaxe-glitch]

@wowamaxe-glitch has applied to work on this issue as part of the Stellar Wave Program's 6th wave.

I'm a full-stack developer and I'd like to take this issue.
I understand the requirements and will follow the existing project structure, keep the implementation clean, and include proper tests where applicable.

ETA: 1–3 days (depending on scope)

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Congratulations, @wowamaxe-glitch! 🎉 Your application was accepted by the repo's maintainers, and the issue is due on June 30, 2026.

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