[OkeA-dev]

Implements issue #1697: streaming milestones that vest linearly and let the freelancer withdraw accrued pay.

Closes #1697

Summary

• Add create_stream(client, freelancer, token, amount, start, end) -> u64: creates a one-milestone escrow and stores DataKey::Stream { start, end, withdrawn, stopped_at }. Requires start < end and end - start >= 3600, else EscrowError::InvalidSchedule (appended at the end).
• Add vested(id) -> i128: amount * (min(now, stop_or_end) - start) / (end - start) clamped to [0, amount], computed overflow-safely.
• Add withdraw_vested(id): freelancer auth, requires escrow Funded and stream not stopped, requires fully funded; pays vested - withdrawn; when fully vested and withdrawn marks milestone released and escrow Completed. Emits ("stream_wd", id) -> amount.
• Add stop_stream(id): client auth, requires Funded and not stopped, requires fully funded; sets stopped_at = now, pays vested-but-unwithdrawn to freelancer, refunds unvested remainder to client, marks status Cancelled. Emits ("stream_st", id) -> (to_freelancer, to_client).
• release_milestone and cancel_contract return InvalidStatus on stream escrows (streams use their own functions).
• Add get_stream(id).
• EscrowError::InvalidSchedule = 20 appended at the end (no renumbering).

Security checklist

• Can the freelancer withdraw more than vested? No. withdraw_vested computes vested from time/stop and pays only vested - withdrawn; checks reject if vested <= withdrawn or nothing to withdraw.
• Can stopping a stream claw back vested pay? No. stop_stream pays vested - withdrawn to the freelancer (and only refunds unvested remainder to the client). Vested amounts are not clawed back.

WASM size

• Before (origin/main c970981): 38,481 bytes
• After (this PR): 46,372 bytes
• Delta: +7,891 bytes (+20.5%) — under 128 KB

Full cargo test output

    Finished `test` profile [unoptimized + debuginfo] target(s) in 0.36s
     Running unittests src/lib.rs (target/debug/deps/escrow-a002c7a24891b423)

running 13 tests
test test::initialize_only_once ... ok
test test::non_admin_cannot_void_rating ... ok
test test::full_happy_path ... ok
test test::cancel_unfunded_escrow_does_not_count_cancellation ... ok
test test::pause_blocks_mutations ... ok
test test::dispute_split_and_cancel ... ok
test test::ratings_issued_before_upgrade_return_rating_not_found ... ok
test test::dispute_outcomes_freelancer_client_and_exact_threshold ... ok
test test::rate_then_void_restores_reputation_and_prevents_rerating ... ok
test test::rejects_overfunding_and_double_release ... ok
test test::void_unrated_escrow_fails_with_rating_not_found ... ok
test test::rate_resolved_escrow_succeeds_once_and_cancelled_rejected ... ok
test test::void_one_of_three_ratings_preserves_others ... ok

test result: ok. 13 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out; finished in 0.65s

Docs

• README.md updated with new functions (create_stream, vested, withdraw_vested, stop_stream, get_stream) and InvalidSchedule error.

[mikewheeleer]

hey @OkeA-dev 👋 this PR scans clean and CI is green, but it now has merge conflicts with main — please rebase on the latest main and push, and we'll merge it 🙌

[mikewheeleer]

tidy work — thanks for this!