hbc/server: request InfoPlugin refresh when host has no plugin data; update docs

- Server sets request_update=1 in ACK when host.plugin_data is empty
- hbc: AsyncConnection.request_info_event; handle_ack sets it on request_update
- hbc: _info_plugin_refresh_loop clears InfoPlugin caches and resends on demand
- hbc_mini: same via _request_info event and _info_refresh_loop
- docs/USERS.md: document client-declared owner config key
- docs/PLUGIN_DEVELOPMENT.md: document server-initiated InfoPlugin refresh

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

hbd/client/main.py

@@ -59,6 +59,7 @@ class AsyncConnection:
         self._dead = False
         self._ever_opened = False
         self._open_fail_count = 0   # consecutive failures before first success
+        self.request_info_event: asyncio.Event = asyncio.Event()
 
         self.logger = logging.getLogger(f"hbc.conn.{addr}")
 
@@ -138,6 +139,9 @@ class AsyncConnection:
         
         self.ackcount += 1
         self.logger.debug(f"ACK received, RTT: {rtt:.1f}ms")
+        if msg.get("request_update"):
+            self.logger.info("server requested plugin info refresh")
+            self.request_info_event.set()
 
 
 class HeartbeatProtocol(asyncio.DatagramProtocol):
@@ -338,15 +342,35 @@ async def heartbeat_sender(conn: AsyncConnection, interval: int):
             raise
 
 
+async def _info_plugin_refresh_loop(conn: AsyncConnection, info_plugins: List):
+    """Wait for server requests to re-send InfoPlugin data."""
+    logger = logging.getLogger("hbc.plugins")
+    while running:
+        await conn.request_info_event.wait()
+        if not running:
+            break
+        conn.request_info_event.clear()
+        logger.info("refreshing InfoPlugins on server request")
+        for plugin in info_plugins:
+            plugin._cache = None
+            try:
+                data = await plugin.collect()
+                if data:
+                    await conn.sendto({"plugin": plugin.name, **data}, "PLG")
+                    logger.info(f"Resent {plugin.name} data")
+            except Exception as e:
+                logger.error(f"Error re-collecting {plugin.name}: {e}", exc_info=True)
+
+
 async def plugin_collector(conn: AsyncConnection, registry: PluginRegistry):
     """Collect and send plugin data.
-    
+
     Args:
         conn: Connection to send on
         registry: Plugin registry
     """
     logger = logging.getLogger("hbc.plugins")
-    
+
     # Collect InfoPlugins once at startup
     info_plugins = registry.get_by_type(InfoPlugin)
     for plugin in info_plugins:
@@ -359,34 +383,31 @@ async def plugin_collector(conn: AsyncConnection, registry: PluginRegistry):
                 logger.info(f"Sent {plugin.name} data")
         except Exception as e:
             logger.error(f"Error collecting {plugin.name}: {e}", exc_info=True)
-    
+
     # Schedule MonitorPlugins
     # Group plugins by interval
     from collections import defaultdict
     by_interval = defaultdict(list)
-    
+
     monitor_plugins = registry.get_by_type(MonitorPlugin)
     for plugin in monitor_plugins:
         by_interval[plugin.interval].append(plugin)
-    
-    # Create tasks for each interval
-    tasks = []
+
+    # Create tasks for each interval; always include the info-refresh watcher
+    tasks = [asyncio.create_task(_info_plugin_refresh_loop(conn, info_plugins))]
     for interval, plugins in by_interval.items():
-        task = asyncio.create_task(
+        tasks.append(asyncio.create_task(
             plugin_collector_interval(conn, plugins, interval)
-        )
-        tasks.append(task)
-    
-    # Wait for all tasks
-    if tasks:
-        try:
-            await asyncio.gather(*tasks, return_exceptions=True)
-        except asyncio.CancelledError:
-            logger.debug("Plugin collector cancelled, cancelling sub-tasks")
-            for task in tasks:
-                if not task.done():
-                    task.cancel()
-            raise
+        ))
+
+    try:
+        await asyncio.gather(*tasks, return_exceptions=True)
+    except asyncio.CancelledError:
+        logger.debug("Plugin collector cancelled, cancelling sub-tasks")
+        for task in tasks:
+            if not task.done():
+                task.cancel()
+        raise
 
 
 async def plugin_collector_interval(