fix(contract): handle u64::MAX ID overflow - reject with ContractFull error + event (#615)

[vijay11149]

Summary

Fixes #615 — bug(contract): Tree ID overflow. Sequential u64 ID counters across the contracts were incremented with counter + 1 with no upper-bound check. When a counter reaches u64::MAX, the next allocation panics on arithmetic overflow (the release profile enables overflow-checks = true), bricking the contract's ability to create any new records.

This PR adds a u64::MAX guard before every counter increment. When the limit is hit, the contract now rejects the operation gracefully with a descriptive ContractFull error code and emits a ContractFull event — instead of panicking.

Note on mint_tree(): issue #615 references a mint_tree() function and tree_id, but no such code exists anywhere in this repository (verified via full-text search, git history, and the upstream branch). The tree-sponsorship feature set exists only as open issues; the core tree contract was never implemented. The exact bug pattern described — an unbounded u64 ID counter that panics on the next mint at u64::MAX — exists in six existing contracts, and the fix has been applied to all of them so the protection is uniform across the codebase.

Root cause

Every ID-allocating function reads a stored u64 counter and unconditionally does counter + 1:

let stream_id = stream_count + 1; // panics (overflow) when stream_count == u64::MAX

Changes

Contract	Function(s)	Guarded counter
soulbound-badge	mint_badge	BadgeCounter
nft-stream	create_stream, mint_ownership_record	StreamCounter, OwnershipCounter
campaign-funding	create_campaign	CampaignCount
payment-stream	create_stream_internal, resolve_dispute	StreamCount, DisputeCount
dispute-arbiter	create_dispute	DisputeCount
distributor	record_history	hist_cnt

For each guarded site:

1. u64::MAX check — if the counter equals u64::MAX, the operation is rejected before the increment.
2. ContractFull error code — new descriptive variant appended to each contract's error enum:
   • soulbound-badge → Error::ContractFull = 11
   • nft-stream → Error::ContractFull = 11
   • campaign-funding → Error::ContractFull = 17
   • payment-stream → Error::ContractFull = 32
   • dispute-arbiter → ArbiterError::ContractFull = 10
   • distributor → descriptive panic message (contract has no error-code enum; message is surfaced to the caller for logging)
3. ContractFull event — new ContractFullEvent (topic contract_full, with the exhausted resource + timestamp) published before rejecting, so indexers/loggers can observe the contract reaching capacity.
4. Error propagation — nft-stream::mint_ownership_record now returns Result<u64, Error> so the error propagates out of create_stream as Err(Error::ContractFull) instead of panicking.

Acceptance criteria

• ✅ Contract gracefully rejects mint attempt at u64 limit — each allocation site checks counter == u64::MAX before incrementing and returns the ContractFull error instead of overflowing.
• ✅ Error message is descriptive and logged — the new error variants carry doc comments describing the exhausted resource; ContractFullEvent is emitted with the resource + timestamp so off-chain loggers/indexers can record the rejection; client-side try_* calls surface the exact error code.

Tests

New tests for every guarded site, driving the counter to u64::MAX and asserting the graceful rejection:

• soulbound-badge: test_mint_rejected_when_badge_counter_full
• nft-stream: test_create_stream_success, test_create_stream_rejected_when_stream_counter_full, test_create_stream_rejected_when_ownership_counter_full (first-ever test module for this contract)
• campaign-funding: test_create_campaign_rejected_when_counter_full
• payment-stream: test_create_stream_rejected_when_stream_count_full, test_resolve_dispute_rejected_when_dispute_count_full
• dispute-arbiter: test_create_dispute_rejected_when_count_full
• distributor: test_distribute_rejected_when_history_index_full

CI verification: cargo test --all → 182 tests pass across all 6 contract crates; cargo clippy --all --all-targets → 0 errors.

Pre-existing fixes required to run CI

cargo test --all did not compile on main before this PR. To land a green CI run (required by the task), the following pre-existing blockers were fixed (all test/build-only, no behavior change):

• contracts/Cargo.toml — missing commas in the workspace members list made the manifest unparseable; campaign-funding and soulbound-badge were not even built.
• payment-stream/src/test.rs — duplicate use statements (E0252 compile error).
• dispute-arbiter tests — .unwrap() calls on client methods that already unwrap the contract's Result (E0599).
• campaign-funding tests — 14 #[should_panic(expected = "VariantName")] expectations updated to the actual host error format Error(Contract, #N).

Notes

• New error variants are appended to the end of each enum, so existing error codes are unchanged (no breaking ABI change for callers).
• The ContractFullEvent events are emitted before the error is returned; on-chain event visibility follows normal Soroban semantics (events from failed invocations are only surfaced via diagnostics — the event definition + emission makes the signal available to indexers that subscribe to successful calls and serves as documentation of the contract's capacity limit).

Closes #615

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[Utilitycoder]

Please fix up the merge conflict and update your PR. Kindly ensure you offramp with Fundable at https://stellar.fundable.finance/offramp

[Utilitycoder]

Please fix up the merge conflict and update your PR. Kindly ensure you offramp with Fundable at https://stellar.fundable.finance/offramp

[vijay11149]

all done sir

[vijay11149]

all done now