fix: use real block height for startup sync and non-blocking background_tick

- Startup sync was hardcoded to block_height=120, epoch=0. Now reads
  the actual bittensor_block from state_manager so WASM challenges can
  correctly detect block_height % N == 0 for periodic GitHub refresh.
- background_tick now uses try_lock instead of lock on the persistent
  WASM instance, skipping gracefully when sync() holds the mutex.
  This prevents background_tick from delaying higher-priority sync calls.

Author: factorydroid

bins/validator-node/src/main.rs

@@ -1115,13 +1115,15 @@ async fn main() -> Result<()> {
             }
 
             // Run sync() on each challenge at startup
+            let startup_block = state_manager.apply(|state| state.bittensor_block);
+            let startup_epoch = if startup_block > 0 { startup_block / 360 } else { 0 };
             for (challenge_id, module_path) in &challenges {
                 let mp = if module_path.is_empty() {
                     challenge_id.to_string()
                 } else {
                     module_path.clone()
                 };
-                match executor.execute_sync_with_block(&mp, 120, 0) {
+                match executor.execute_sync_with_block(&mp, startup_block, startup_epoch) {
                     Ok(result) => {
                         info!(
                             challenge_id = %challenge_id,

bins/validator-node/src/wasm_executor.rs

@@ -1507,14 +1507,21 @@ impl WasmChallengeExecutor {
 
     /// Execute background_tick() on the persistent WASM instance.
     /// Called every block for lightweight background work.
+    /// Uses try_lock to avoid blocking sync() which has higher priority.
     pub fn execute_background_tick(
         &self,
         module_path: &str,
         block_height: u64,
         epoch: u64,
     ) -> Result<()> {
         let pi = self.get_or_create_persistent(module_path, block_height, epoch)?;
-        let mut guard = pi.lock();
+        let mut guard = match pi.try_lock() {
+            Some(g) => g,
+            None => {
+                debug!(module = module_path, "background_tick skipped: instance busy (sync in progress)");
+                return Ok(());
+            }
+        };
 
         let real_now_ms = std::time::SystemTime::now()
             .duration_since(std::time::UNIX_EPOCH)