feat: add related_contracts() WASM export, full RelatedContracts API, and proptest fuzzing

[xotatera]

Problem

Contracts that depend on other contracts had no way to declare their dependencies upfront. The runtime had to discover dependencies reactively through ValidateResult::RequestRelated responses, causing unnecessary round-trips. RelatedContractsContainer also lacked depth/cycle tracking, making it vulnerable to infinite loops from malicious or buggy contracts.

Approach

WASM Export for Upfront Dependency Declaration

• New related_contracts() WASM export (zero-arg, returns serialized Vec<RelatedContract>) lets contracts declare dependencies at compile time
• ContractInterface trait gets a default related_contracts() method (returns empty vec)
• freenet-macros generates the FFI wrapper automatically
• inner_related_contracts in wasm_interface.rs handles serialization across the WASM boundary

Full RelatedContracts API

• RelatedContracts: query helpers (len, is_empty, contains, get, insert, resolved_count, pending_count, all_resolved)
• RelatedContract: builder pattern with with_timeout/with_ttl (reserved for future runtime enforcement)
• RelatedMode: derives Copy + Clone for ergonomic use in mock/test code
• ValidateResult: derives Clone (needed by proptest strategies)

RelatedContractsContainer Safety

• request_depth + seen set for depth limiting and cycle detection
• MAX_REQUEST_DEPTH = 10 with documented effective budget
• set_initial_depth() for sharing depth budget across nested resolution
• request_with_tracking() combines depth check + cycle detection
• increment_depth() checks before incrementing (bug found by proptest)
• merge() preserves max depth and unions seen sets
• set_initial_depth() clamps to MAX (bug found by proptest)

Proptest Fuzzing

Property-based tests that already found and fixed 2 bugs:

1. increment_depth() could overshoot MAX_REQUEST_DEPTH when set_initial_depth was called first (incremented before checking)
2. set_initial_depth() accepted values above MAX without clamping

12 proptest tests covering:

• Serde round-trips: UpdateData (all 6 variants), ValidateResult, RelatedContracts, RelatedContract
• into_owned() preserves serialized form
• Query invariants: resolved_count + pending_count == len
• Container op sequences: depth never exceeds MAX under any operation ordering
• Cycle detection: duplicate requests always fail
• Merge: depth = max, seen = union
• From<RelatedContracts> splits resolved/not_found correctly
• From<Vec<UpdateData>> extracts only RelatedState variants

Testing

• 25 lib tests pass (including 12 new proptest tests)
• cargo fmt && cargo clippy clean
• Proptest default 256 cases per test; verified with PROPTEST_CASES=1000

Files Changed

File	Changes
rust-macros/src/contract_impl.rs	Generate related_contracts() FFI export
rust/Cargo.toml	Add proptest dev-dependency
rust/src/contract_composition.rs	Add related_contracts() to ContractComponent trait
rust/src/contract_interface/encoding.rs	Depth/cycle tracking, container API, proptest module
rust/src/contract_interface/trait_def.rs	Add related_contracts() to ContractInterface
rust/src/contract_interface/update.rs	Query helpers, builder pattern, Clone on ValidateResult, proptest module
rust/src/contract_interface/wasm_interface.rs	inner_related_contracts WASM boundary helper
rust/src/memory.rs	wasm_return_0arg for zero-arg WASM exports

[AI-assisted - Claude]

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