fix: sessions paginationとhealth診断を改善

- sessions cursorのエンコード不具合と長いsession IDのバッファ問題を修正
- response budgetに基づくsessionsページングを追加
- get_system_healthにsession_countを追加
- metadata_jsonのフィールド別エラー診断を追加
- CRUD互換性とDebug/Release/ASanテストを確認

1 files changed, 7 insertions, 0 deletions

diff --git a/src/mcp/tools/get_system_health.c b/src/mcp/tools/get_system_health.c
index 893a3b1..4189db3 100644
--- a/src/mcp/tools/get_system_health.c
+++ b/src/mcp/tools/get_system_health.c
@@ -15,6 +15,11 @@ call_get_system_health(const mcpc_tool_t *tool, mcpc_ucbr_t *result)
       tiny_mcp_tool_add_error(result, "INTERNAL_ERROR", "tool context is unavailable");
       return;
     }
+  if (!tiny_mcp_tools_ensure_history_index(context) || !context->history_index)
+    {
+      tiny_mcp_tool_add_error(result, "INTERNAL_ERROR", "history index allocation failed");
+      return;
+    }
   tiny_store_health(context->store, &health);
   tiny_json_init(&json);
   tiny_json_raw(&json, "{\"status\":");
@@ -27,6 +32,8 @@ call_get_system_health(const mcpc_tool_t *tool, mcpc_ucbr_t *result)
   tiny_json_u64(&json, health.snapshot_size);
   tiny_json_raw(&json, ",\"active_messages\":");
   tiny_json_u64(&json, health.active_messages);
+  tiny_json_raw(&json, ",\"session_count\":");
+  tiny_json_u64(&json, tiny_history_index_session_count(context->history_index));
   tiny_json_raw(&json, ",\"deleted_messages\":");
   tiny_json_u64(&json, health.deleted_messages);
   tiny_json_raw(&json, ",\"last_sequence\":");