feat(discovery-core): add outgoing state sync orchestrator

[m-kus]

TL;DR

Added outgoing state sync orchestration to the discovery module, enabling hierarchical discovery of outgoing channels, subchannels, and note indices.

What changed?

• Created a new outgoing_state.rs module that orchestrates the outgoing sync process
• Implemented sync_outgoing_state function that composes paginated discovery of channels, subchannels, and note indices
• Added concurrent processing of channels and subchannels using FuturesUnordered
• Implemented cursor-based pagination to handle large datasets efficiently
• Added support for precomputing channels for requested recipients
• Exposed the new module via pub mod outgoing_state in the sync module

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This change is 

[m-kus]

• feat(e2e): starknet integration demo explorer #467 : 3 dependent PRs (#480 , #502 , #512 )
• feat(discovery-service): add fallback for chain state, e2e test in the starknet integration environment #466
• feat(e2e): add indexer e2e test suite with sdk devnet helpers #486
• feat(sdk): add indexer discovery provider #485
• feat(discovery-service): add preflight check endpoint #484
• feat(discovery-service): add outgoing state sync endpoint #483
• feat(discovery-service): add incoming sync endpoint with validation and error handling #482
• feat(discovery-service): centralize configuration into config module #481
• feat(discovery-core): add transfer preflight check #474
• feat(discovery-core): add outgoing state sync orchestrator #473 👈 (View in Graphite)
• feat(discovery-core): add incoming state sync orchestrator #472
• feat(discovery-core): add paginated last-note-index search with bisection #471
• feat(discovery-core): add paginated outgoing channel discovery #470
• refactor: propagate compliance-to-auditor rename and fee params to sdk and rust #505
• main

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[Yoni-Starkware]

@Yoni-Starkware reviewed 2 files and all commit messages, and made 3 comments.
Reviewable status: all files reviewed, 2 unresolved discussions (waiting on m-kus).

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crates/discovery-core/src/sync/outgoing_state.rs line 96 at r1 (raw file):

    // On a fresh cursor this is vacuously true; on subsequent calls it fires
    // once all previously discovered channels have been fully processed.
    let mut channels = if cursor.all_channels_processed() {

etc. (to emphasize they are brand new channels, and not existing ones that were partially traversed)

Suggestion:

 let mut new_channels

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crates/discovery-core/src/sync/outgoing_state.rs line 190 at r1 (raw file):

    budget: &IoBudget,
) -> Result<ProcessChannelResult, DiscoveryError> {
    let channel_key = cursor.channel_key.ok_or_else(|| {

Why is the channel key optional?

Code quote:

let channel_key = cursor.channel_key.ok_or_else(|| 

[m-kus]

@m-kus resolved 2 discussions.
Reviewable status: 1 of 8 files reviewed, all discussions resolved (waiting on Yoni-Starkware).