test(wasm-challenge): add comprehensive WASM challenge integration tests with 5-validator consensus

Add 18 integration tests in tests/wasm_challenge_tests.rs covering:

WASM Module Tests (3):
- Compilation of term-challenge WASM binary via WasmRuntime
- Instantiation with InstanceConfig and InMemoryStorageBackend
- Verification of expected exports (memory)

Challenge Lifecycle Tests (6):
- Sudo owner adds challenge with real WASM binary
- Sudo owner removes challenge and verifies cleanup
- Non-sudo key rejected via signed message authorization check
- Challenge persistence in sled storage (save/load roundtrip)
- State hash changes on challenge add/remove
- Challenge deletion from storage

Consensus Tests (4):
- 5-validator ConsensusEngine setup with quorum=3
- Leader creates proposal with ChallengeSubmission type
- StateManager add/remove challenges
- Challenge survives epoch transitions

Full Pipeline Tests (5):
- Multiple challenges lifecycle (add 3, remove selectively)
- Full evaluation pipeline: add -> persist -> load -> compile -> instantiate
- All 5 validators instantiate WASM from stored challenge
- Full PBFT round: proposal -> pre-prepare -> handle_proposal -> prepares
- State serialization/deserialization roundtrip with WASM challenge

Key implementation details:
- Each ConsensusEngine gets its own ValidatorSet for correct leader identity
- Uses ChallengeSubmission (not ConfigUpdate) to avoid sudo auth at consensus level
- Real 302KB term-challenge WASM binary loaded via include_bytes!()
- Added wasm-runtime-interface and sha2 dependencies to tests/Cargo.toml

Author: echobt

Cargo.lock

@@ -40,12 +40,17 @@ path = "blockchain_state_tests.rs"
 name = "checkpoint_tests"
 path = "checkpoint_tests.rs"
 
+[[test]]
+name = "wasm_challenge_tests"
+path = "wasm_challenge_tests.rs"
+
 [dependencies]
 platform-core = { path = "../crates/core" }
 platform-storage = { path = "../crates/storage" }
 platform-p2p-consensus = { path = "../crates/p2p-consensus" }
 platform-bittensor = { path = "../crates/bittensor-integration" }
 platform-challenge-sdk = { path = "../crates/challenge-sdk" }
+wasm-runtime-interface = { path = "../crates/wasm-runtime-interface" }
 
 tokio = { version = "1.40", features = ["full", "test-util"] }
 tempfile = "3.12"
@@ -58,5 +63,6 @@ rand = "0.8"
 lz4_flex = "0.11"
 hex = "0.4"
 bincode = "1.3"
+sha2 = { workspace = true }
 reqwest = { workspace = true }
 sp-core = { workspace = true }