feat(#182): unsubscribe + deterministic ids for per-trade subscriptions

[codaMW]

Closes the subscription-lifecycle half of #182 (the request_id half was done via #172; the chat side via #247).

Problem

subscribe_gift_wraps and subscribe_single_order (orders.rs) called client.subscribe(filter, None) with auto-generated ids and never unsubscribed, so the relay-side subscription outlived the event loop's exit (30-min idle timeout, shutdown, or completed trade). Every create/take spawned a new one they accumulated over a long session (bandwidth, duplicate notifications, relay pressure on mobile).

Fix

Mirrors the subscribe_incoming_chat pattern that #247 established:

• Deterministic ids (trade_subscription_id / single_order_subscription_id) via subscribe_with_id, so a repeat subscribe for the same trade/order replaces in place instead of stacking. Full pubkey hex (not an 8-char prefix) to rule out collisions.
• unsubscribe(&sub_id) at each loop's single exit point, so the relay-side subscription never outlives the task.

The limit(0) live-only replay-protection of subscribe_gift_wraps is unchanged only the subscription id changes, not the filter.

Scope

Central subscription registry deferred per the issue's own guidance (nostr-sdk re-establishes subscriptions on reconnect).

Tests

• Unit tests for the deterministic-id logic: idempotent per pubkey, no cross-pubkey collision, expected format.
• Unsubscribe-on-exit is covered by inspection at each single exit point, mirroring the proven subscribe_incoming_chat cleanup, since exercising it needs a live relay.
• cargo test (213 passing), clippy -D warnings, flutter analyze all clean.

Summary by CodeRabbit

• Bug Fixes

  • Improved reliability of order updates by preventing duplicate or stale subscriptions.
  • Ensured background watchers clean up subscriptions when they stop, time out, or shut down.
  • Stabilized repeated subscription and resubscription behavior to reduce missed updates and resource leaks.

• Tests

  • Added coverage for consistent subscription identification and safe watcher replacement.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: 84bf34fa-045c-41ec-ad3a-1e2a4a530dba

📥 Commits

Reviewing files that changed from the base of the PR and between aef6a17 and 1397ea8.

📒 Files selected for processing (1)

• rust/src/api/orders.rs

🚧 Files skipped from review as they are similar to previous changes (1)

• rust/src/api/orders.rs

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Walkthrough

Relay watchers now use deterministic SubscriptionId values for gift-wrap and single-order subscriptions. Generation tracking prevents stale watchers from unsubscribing replacement subscriptions. Tests cover identifier formatting, uniqueness, generation advancement, and cleanup ownership.

Changes

Relay subscription lifecycle

Layer / File(s)	Summary
Deterministic identifiers and ownership tracking rust/src/api/orders.rs	Helper functions generate deterministic trade and order subscription IDs. Generation tracking identifies the current subscription owner. Tests verify formatting, uniqueness, generation advancement, and stale-watcher cleanup prevention.
Gift-wrap watcher lifecycle rust/src/api/orders.rs	subscribe_gift_wraps uses a deterministic per-trade ID and unsubscribes on exit only when it owns the current subscription generation.
Single-order watcher lifecycle rust/src/api/orders.rs	subscribe_single_order uses a deterministic per-order ID and conditionally unsubscribes on exit only when it remains the current owner.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Possibly related issues

• MostroP2P/app issue 182 — Covers deterministic subscription IDs and explicit unsubscription in rust/src/api/orders.rs.

Poem

I’m a rabbit watching relays run,
Stable IDs for every one.
New watchers claim their proper place,
Old watchers yield with careful grace.
Stale paws cannot undo the tune—
Clean subscriptions beneath the moon.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly summarizes the main changes: unsubscribe behavior and deterministic IDs for per-trade subscriptions.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 2

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
rest with a brief reason, keep changes minimal, and validate.

Inline comments:
In `@rust/src/api/orders.rs`:
- Around line 3073-3097: Add an asynchronous lifecycle regression test near
trade_subscription_id_is_deterministic_and_per_pubkey and
single_order_subscription_id_matches_expected_format that starts watcher A,
replaces it with watcher B for the same trade or order, waits for A to exit, and
verifies B remains subscribed. Exercise the existing watcher replacement/cleanup
APIs and assert the active subscription state after cleanup, without changing
the subscription ID construction tests.
- Around line 1503-1509: Make deterministic subscription cleanup
generation-aware: in rust/src/api/orders.rs lines 1503-1509, update the
gift-wrap watcher cleanup to unsubscribe only when its task still owns the
current generation or serialized subscription; in lines 2379-2382, apply the
same ownership guard to single-order cleanup. Before starting each replacement
watcher, cancel and await the existing task so stale tasks cannot unsubscribe
the replacement subscription.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro Plus

Run ID: c4129d97-788c-41fa-a319-b98472aebb60

📥 Commits

Reviewing files that changed from the base of the PR and between c0608d7 and 0989769.

📒 Files selected for processing (1)

• rust/src/api/orders.rs

[codaMW]

@grunch Rebased onto current main (resolved parallel test-module conflicts from the dispute PRs). Heads-up on scope: CodeRabbit found a real stale-task-unsubscribe hazard that the deterministic ids introduced, so this now carries a small per-id generation guard to make cleanup ownership-aware a bit more than #182's minimal ask. If you'd rather keep it lean, the alternative is unique (auto) ids + unconditional self-unsubscribe, which fixes the leak without the guard but drops the re-subscribe dedup. Happy to go either way. Green on cargo test (237) / clippy / flutter analyze.