feat: announcement purgatory

Extends purgatory to hold repository announcements until git data arrives,
preventing empty repositories from being served to clients.

When an announcement is received, a bare repo is created immediately and the
announcement is held in purgatory. It is only promoted and served once a git
push confirms real content exists. If no push arrives before expiry, the bare
repo is deleted and the announcement is silently discarded.

Key behaviours:
- Soft expiry: announcements are hidden from clients but kept alive while git
  pushes are in progress, reviving on successful push
- Expiry is extended when a matching state event or git push is observed
- NIP-09 deletion events remove announcements from purgatory
- Purgatory state (announcements, state events, PR events, expired set) is
  persisted to disk on graceful shutdown and restored on startup, with elapsed
  downtime subtracted from expiry deadlines
- Purgatory announcements drive StateOnly sync in the sync system so state
  events are fetched from listed relays before promotion
- SyncLevel added to RepoSyncIndex to distinguish purgatory repos (StateOnly)
  from promoted repos (Full L2+L3 sync)

1 files changed, 31 insertions, 2 deletions

diff --git a/src/nostr/builder.rs b/src/nostr/builder.rs
index 713c129..7a05348 100644
--- a/src/nostr/builder.rs
+++ b/src/nostr/builder.rs
@@ -14,10 +14,11 @@ use nostr_relay_builder::prelude::*;
 use crate::config::{Config, DatabaseBackend};
 use crate::nostr::events::RepositoryAnnouncement;
 use crate::nostr::policy::{
-    AnnouncementPolicy, AnnouncementResult, PolicyContext, PrEventPolicy, ReferenceResult,
-    RelatedEventPolicy, StatePolicy, StateResult,
+    AnnouncementPolicy, AnnouncementResult, DeletionPolicy, PolicyContext, PrEventPolicy,
+    ReferenceResult, RelatedEventPolicy, StatePolicy, StateResult,
 };
 
+
 /// Type alias for the shared database used by the relay
 pub type SharedDatabase = Arc<dyn NostrDatabase>;
 
@@ -28,6 +29,7 @@ pub type SharedDatabase = Arc<dyn NostrDatabase>;
 /// - `StatePolicy` - State event validation + ref alignment
 /// - `PrEventPolicy` - PR/PR Update validation
 /// - `RelatedEventPolicy` - Forward/backward reference checking
+/// - `DeletionPolicy` - NIP-09 event deletion request handling
 ///
 /// Uses stateful database queries to check event relationships.
 #[derive(Clone)]
@@ -37,6 +39,7 @@ pub struct Nip34WritePolicy {
     state_policy: StatePolicy,
     pr_event_policy: PrEventPolicy,
     related_event_policy: RelatedEventPolicy,
+    deletion_policy: DeletionPolicy,
 }
 
 impl std::fmt::Debug for Nip34WritePolicy {
@@ -68,6 +71,7 @@ impl Nip34WritePolicy {
             state_policy: StatePolicy::new(ctx.clone()),
             pr_event_policy: PrEventPolicy::new(ctx.clone()),
             related_event_policy: RelatedEventPolicy::new(ctx.clone()),
+            deletion_policy: DeletionPolicy::new(ctx.clone()),
             ctx,
         }
     }
@@ -205,6 +209,30 @@ impl Nip34WritePolicy {
                     }
                 }
             }
+            AnnouncementResult::AcceptPurgatory => {
+                // New announcement - add to purgatory
+                match self.announcement_policy.add_to_purgatory(event) {
+                    Ok(()) => {
+                        tracing::info!(
+                            "Accepted announcement to purgatory: {} (waiting for git data)",
+                            event_id_str
+                        );
+
+                        WritePolicyResult::Reject {
+                            status: true, // Client sees OK
+                            message: "purgatory: won't be served until git data arrives".into(),
+                        }
+                    }
+                    Err(e) => {
+                        tracing::warn!(
+                            "Failed to add announcement to purgatory {}: {}",
+                            event_id_str,
+                            e
+                        );
+                        WritePolicyResult::reject(e)
+                    }
+                }
+            }
             AnnouncementResult::AcceptMaintainer => {
                 // Parse announcement to get details for logging
                 match RepositoryAnnouncement::from_event(event.clone()) {
@@ -621,6 +649,7 @@ impl WritePolicy for Nip34WritePolicy {
                     );
                     WritePolicyResult::Accept
                 }
+                Kind::EventDeletion => self.deletion_policy.handle(event).await,
                 _ => self.handle_related_event(event, "Event").await,
             }
         })