server: event file plain read now uses per-fid subscription

Plain reads (without writing a filter first) now get a per-fid
subscription with '*' filter, identical to 'echo * | rdwrs event'.

This fixes event loss — the old EventStream path overwrote events
when multiple arrived before the reader consumed them.

cmd/olliesrv/server.go

@@ -598,7 +598,7 @@ func read(root *fs.Tree, cs *connState, fc *plan9.Fcall, ctx context.Context) *p
 	}
 
 	if entry.StreamMode() {
-		// Special handling for event file with filter
+		// Special handling for event file — always use per-fid subscription
 		if path == "event" {
 			cs.mu.RLock()
 			f, fidOK := cs.fids[fc.Fid]
@@ -609,38 +609,39 @@ func read(root *fs.Tree, cs *connState, fc *plan9.Fcall, ctx context.Context) *p
 				eventCh := f.eventCh
 				f.mu.Unlock()
 
-				// If filter was written, use filtered subscription
-				if filter != "" && eventCh == nil {
-					// Create subscription on first read after write
+				// Create subscription on first read (filter defaults to "*" for all events)
+				if eventCh == nil {
+					if filter == "" {
+						filter = "*"
+					}
 					subCtx, cancel := context.WithCancel(ctx)
 					ch := session.SubscribeEventsFiltered(subCtx, filter)
 					f.mu.Lock()
+					f.eventFilter = filter
 					f.eventCh = ch
 					f.eventCancel = cancel
 					f.mu.Unlock()
 					eventCh = ch
 				}
 
-				if eventCh != nil {
-					// Read from filtered subscription
-					select {
-					case ev, ok := <-eventCh:
-						if !ok {
-							return &plan9.Fcall{Type: plan9.Rread, Tag: fc.Tag, Count: 0}
-						}
-						line := ev.Topic
-						if ev.Payload != "" {
-							line += " " + ev.Payload
-						}
-						content := []byte(line + "\n")
-						count := int(fc.Count)
-						if count > len(content) {
-							count = len(content)
-						}
-						return &plan9.Fcall{Type: plan9.Rread, Tag: fc.Tag, Count: uint32(count), Data: content[:count]}
-					case <-ctx.Done():
-						return errFcall(fc, "interrupted")
+				// Read from subscription — blocks until event arrives
+				select {
+				case ev, ok := <-eventCh:
+					if !ok {
+						return &plan9.Fcall{Type: plan9.Rread, Tag: fc.Tag, Count: 0}
 					}
+					line := ev.Topic
+					if ev.Payload != "" {
+						line += " " + ev.Payload
+					}
+					content := []byte(line + "\n")
+					count := int(fc.Count)
+					if count > len(content) {
+						count = len(content)
+					}
+					return &plan9.Fcall{Type: plan9.Rread, Tag: fc.Tag, Count: uint32(count), Data: content[:count]}
+				case <-ctx.Done():
+					return errFcall(fc, "interrupted")
 				}
 			}
 		}