feat: upgrade repo to Full sync and trigger PR event subscription after announcement promotion

When git data arrives for a purgatory announcement and promotes it to the
database, the relay now:

1. Upgrades the announcement's sync level in RepoSyncIndex from StateOnly
   to Full (git/sync.rs: process_purgatory_announcements)
2. Sends AddFilters actions to SyncManager for all connected relays, using
   Full sync filters (Layer 2 #a/#A/#q) to subscribe to PR events
   (purgatory/sync/context.rs: RealSyncContext.process_newly_available_git_data)
3. For user-submitted purgatory announcements, registers the repo in
   RepoSyncIndex with StateOnly level and sends AddFilters to SyncManager
   so it discovers and connects to relays listed in the announcement tags
   (nostr/builder.rs: handle_announcement AcceptPurgatory path)

The RealSyncContext now accepts optional repo_sync_index and sync_action_tx
parameters. main.rs wires these up from SyncManager. PolicyContext gains
repo_sync_index and sync_action_tx fields for the write policy path.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/git/handlers.rs b/src/git/handlers.rs
index 017eee4..129ca2c 100644
--- a/src/git/handlers.rs
+++ b/src/git/handlers.rs
@@ -307,6 +307,7 @@ pub async fn handle_receive_pack(
         Some(&relay),
         &purgatory,
         git_data_path_buf,
+        None,
     )
     .await
     {