test: implement property-based fuzz tests for all Soroban contracts

[bbkenny]

This PR adds property-based fuzz tests to all Stellar Soroban contracts in the workspace using the proptest framework.

Key changes:

• Integrated proptest into the workspace and individual contract crates.
• Added test_announce_fuzz to stealth-announcer to verify event emission integrity with arbitrary inputs.
• Added test_registry_fuzz to stealth-registry to verify data persistence for arbitrary schemes and meta-addresses.
• Added test_names_fuzz to wraith-names to verify name registration and reverse lookup logic.

These tests help ensure the robustness of the protocol contracts against edge cases and malformed inputs.

Closes #5

[bbkenny]

Hi @wraith-protocol, I've implemented the property-based fuzz tests for all Soroban contracts as requested in issue #5. These tests use the proptest framework to verify contract invariants against arbitrary inputs, significantly improving the robustness of the protocol. Ready for review!

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@bbkenny Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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[truthixify]

Closing this one — issue #5 was already addressed by #13 which landed first and went a bit broader (dedicated tests/properties.rs per crate, a WRAITH_PROPTEST_CASES env knob, and the nightly CI matrix at 16k cases). Your approach (proptests inline in the lib.rs #[cfg(test)] modules) is also valid — sorry the duplication happened, that's on us for not making the assignment-tracking more visible.

Definitely don't want this to be a wasted effort though. A few open issues that would slot in nicely with the same proptest muscle:

• contracts Soroban storage TTL automation for wraith-names entries #17 (Soroban storage TTL automation for wraith-names) — needs adversarial coverage around TTL boundaries
• contracts 1-to-N stealth payment splitter on Stellar #15 (1-to-N stealth payment splitter) — atomicity property tests would be the headline deliverable
• sdk Security audit of stealth-sender Soroban contract #3 (Stellar scalar property fuzz with fast-check) — same spirit, TypeScript side

Thanks for picking this up @bbkenny — pick any of those (or another open Stellar Wave issue) and I'll prioritize the review.