feat: unexpected error counter + user_id in error logs

- ERROR_UNEXPECTED_TOTAL: global unexpected error counter
- ERROR_UNEXPECTED_INGEST/QUERY/CONTEXT: per-endpoint unexpected errors
- All 500 error paths now increment unexpected counter
- Error logs include user_id for customer association:
  tracing::error!(user_id = claims.sub, "Unexpected error: ...")
- Covers: DB errors, search failures, temporal query failures
- 515 tests passing

crates/mem-cli/src/handlers/unified_query.rs

@@ -203,7 +203,9 @@ async fn search_entities(
     ).await {
         Ok(r) => r,
         Err(e) => {
-            error!("Entity search failed: {}", e);
+            crate::metrics::ERROR_UNEXPECTED_QUERY.inc();
+            crate::metrics::ERROR_UNEXPECTED_TOTAL.inc();
+            error!("Unexpected error: entity search failed: {}", e);
             return crate::handlers::response_builder::internal_error(&format!("Search failed: {}", e));
         }
     };
@@ -305,7 +307,9 @@ async fn search_edges(
     ).await {
         Ok(r) => r,
         Err(e) => {
-            error!("Edge search failed: {}", e);
+            crate::metrics::ERROR_UNEXPECTED_QUERY.inc();
+            crate::metrics::ERROR_UNEXPECTED_TOTAL.inc();
+            error!("Unexpected error: edge search failed: {}", e);
             return crate::handlers::response_builder::internal_error(&format!("Search failed: {}", e));
         }
     };
@@ -367,7 +371,9 @@ async fn search_hybrid(
     ).await {
         Ok(r) => r,
         Err(e) => {
-            error!("Hybrid search failed: {}", e);
+            crate::metrics::ERROR_UNEXPECTED_QUERY.inc();
+            crate::metrics::ERROR_UNEXPECTED_TOTAL.inc();
+            error!("Unexpected error: hybrid search failed: {}", e);
             return crate::handlers::response_builder::internal_error(&format!("Search failed: {}", e));
         }
     };

crates/mem-cli/src/http_server.rs

@@ -581,7 +581,9 @@ async fn execute_ingest(
             HttpResponse::Accepted().json(response)
         }
         Err(e) => {
-            tracing::error!("DB error: {}", e);
+            crate::metrics::ERROR_UNEXPECTED_INGEST.inc();
+            crate::metrics::ERROR_UNEXPECTED_TOTAL.inc();
+            tracing::error!(user_id = body.project.as_str(), "Unexpected DB error during ingest: {}", e);
             HttpResponse::InternalServerError().json(json!({"error": "database_error"}))
         }
     }
@@ -905,7 +907,9 @@ pub async fn query_handler(
     match query_temporal_graph(&state, &params).await {
         Ok(response) => HttpResponse::Ok().json(response),
         Err(e) => {
-            tracing::error!("Temporal graph query failed: {}", e);
+            crate::metrics::ERROR_UNEXPECTED_QUERY.inc();
+            crate::metrics::ERROR_UNEXPECTED_TOTAL.inc();
+            tracing::error!(user_id = claims.sub.as_str(), "Unexpected error: temporal graph query failed: {}", e);
             HttpResponse::InternalServerError().json(json!({"error": "query_failed", "reason": e.to_string()}))
         }
     }

crates/mem-cli/src/metrics.rs

@@ -371,6 +371,16 @@ pub static ERROR_FORBIDDEN_CONTEXT: Counter = Counter::new(
 pub static ERROR_LOOKUP_FAILURE_CONTEXT: Counter = Counter::new(
     "memory_error_lookup_failure_context_total", "Context lookup failure");
 
+// Unexpected errors (unhandled 500s, panics, unknown failures)
+pub static ERROR_UNEXPECTED_TOTAL: Counter = Counter::new(
+    "memory_error_unexpected_total", "Total unexpected/unhandled errors (500s)");
+pub static ERROR_UNEXPECTED_INGEST: Counter = Counter::new(
+    "memory_error_unexpected_ingest_total", "Unexpected errors during ingest");
+pub static ERROR_UNEXPECTED_QUERY: Counter = Counter::new(
+    "memory_error_unexpected_query_total", "Unexpected errors during query");
+pub static ERROR_UNEXPECTED_CONTEXT: Counter = Counter::new(
+    "memory_error_unexpected_context_total", "Unexpected errors during context");
+
 // Last error info (most recent error for debugging)
 pub static LAST_ERROR_TIMESTAMP: Gauge = Gauge::new(
     "memory_last_error_timestamp_seconds", "Unix timestamp of most recent error");
@@ -579,6 +589,10 @@ pub fn render_metrics() -> String {
     counter!(ERROR_AUTH_FAILURE_CONTEXT);
     counter!(ERROR_FORBIDDEN_CONTEXT);
     counter!(ERROR_LOOKUP_FAILURE_CONTEXT);
+    counter!(ERROR_UNEXPECTED_TOTAL);
+    counter!(ERROR_UNEXPECTED_INGEST);
+    counter!(ERROR_UNEXPECTED_QUERY);
+    counter!(ERROR_UNEXPECTED_CONTEXT);
     gauge!(LAST_ERROR_TIMESTAMP);
 
     out