Use subscribe:true for GET operations instead of separate SUBSCRIBE

[sanity]

Background

River currently uses subscribe: false for GET operations, followed by a separate SUBSCRIBE request. This pattern was adopted in CLI v0.1.7 (August 2025) based on the belief that "GET with subscribe:true requires performing sub-operations from within the main operation and waiting for them to complete, which was never implemented in Freenet."

Current Behavior

CLI (cli/src/api.rs):

let get_request = ContractRequest::Get {
    key: *contract_key.id(),
    return_contract_code: true,
    subscribe: false,  // Always false, we'll subscribe separately if needed
};

UI (ui/src/components/app/freenet_api/room_synchronizer.rs):

let get_request = ContractRequest::Get {
    key: *contract_key.id(),
    return_contract_code: true,
    subscribe: false,
};

Both then issue a separate SUBSCRIBE request after the GET completes.

Analysis of freenet-core

After reviewing the freenet-core implementation, subscribe:true IS fully implemented:

1. Local GET path (client_events/mod.rs:1126-1143): If contract is found locally and subscribe=true, register_subscription_listener() is called before returning the result.

2. Network GET path (client_events/mod.rs:1259-1277): After starting the GET operation, if subscribe=true, register_subscription_listener() is called immediately.

3. Legacy GET path (client_events/mod.rs:1338-1356): Same pattern - subscription listener is registered after starting the operation.

The subscription is registered optimistically (before the GET result is known), which is actually beneficial - it means no updates can be missed between GET completing and SUBSCRIBE being processed.

Proposed Change

Switch to subscribe: true for GET operations:

let get_request = ContractRequest::Get {
    key: *contract_key.id(),
    return_contract_code: true,
    subscribe: true,  // Subscribe atomically with GET
};

And remove the separate SUBSCRIBE request that follows.

Benefits

1. Reduced round-trips: Single request instead of two sequential requests
2. No race condition: Updates cannot be missed between GET response and SUBSCRIBE request
3. Simpler code: Remove the separate subscription logic after GET
4. Consistency: PUT already uses subscribe: true (api.rs:144)

Considerations

• The subscription is registered before the GET completes, so if the GET fails, the client has a registered listener but no state. This is fine - failed GETs would require user retry anyway.
• Should verify behavior matches expectations in integration tests before merging.

[AI-assisted - Claude]