fix: unify sync state tracking for negentropy and REQ+EOSE paths

When negentropy (NIP-77) sync was enabled, the RelaySyncIndex was never
updated to reflect historical sync completion. This caused the three-way
diff algorithm in compute_actions() to malfunction, leading to:
- Repeated sync attempts for the same items
- Incorrect filter counting for consolidation
- Potential premature relay disconnection

This fix unifies both sync paths (REQ+EOSE and Negentropy) through a
consistent PendingBatch flow:

1. Added SyncMethod enum to distinguish between sync types
2. Updated PendingBatch struct to include sync_method field
3. Extracted confirm_batch() method for unified batch confirmation
4. Modified negentropy_sync_and_process() to:
   - Create a PendingBatch before sync
   - Add batch to pending_sync_index
   - On success: Remove batch and call confirm_batch()
   - On failure: Remove batch without confirming

The confirm_batch() method moves repos and root_events from the batch
to the RelayState.repos and RelayState.root_events, ensuring the
three-way diff works correctly regardless of sync method.

Closes: negentropy-sync-state-tracking.md

1 files changed, 3 insertions, 1 deletions

diff --git a/src/sync/algorithms.rs b/src/sync/algorithms.rs
index 3063516..5b5b520 100644
--- a/src/sync/algorithms.rs
+++ b/src/sync/algorithms.rs
@@ -11,7 +11,7 @@ use std::collections::{HashMap, HashSet};
 
 use nostr_sdk::prelude::*;
 
-use super::{ConnectionStatus, PendingBatch, RelayState};
+use super::{ConnectionStatus, PendingBatch, RelayState, SyncMethod};
 
 // =============================================================================
 // Data Structures
@@ -396,6 +396,7 @@ mod tests {
                     root_events: HashSet::new(),
                 },
                 outstanding_subs: HashSet::new(),
+                sync_method: SyncMethod::ReqEose,
             }],
         );
 
@@ -504,6 +505,7 @@ mod tests {
                     root_events: HashSet::new(),
                 },
                 outstanding_subs: HashSet::new(),
+                sync_method: SyncMethod::ReqEose,
             }],
         );