toolsrv: proc/list now rdwr with agent filtering

Write agent ID to filter, or empty for all. Returns pid\tstate\ttool.
Added ListProcsForAgent to State.

cmd/toolsrv/internal/server/proc.go

@@ -405,11 +405,22 @@ func (st *State) ListProcs() []int {
 // ListProcsWithState returns a formatted list of all processes with their state.
 // Format: "pid\tstate\ttool\n" where state is "running" or "exited (code)".
 func (st *State) ListProcsWithState() string {
+	return st.ListProcsForAgent("")
+}
+
+// ListProcsForAgent returns a formatted list of processes for the given agent.
+// If agentID is empty, returns all processes.
+// Format: "pid\tstate\ttool\n"
+func (st *State) ListProcsForAgent(agentID string) string {
 	st.procMu.Lock()
 	defer st.procMu.Unlock()
 	var buf bytes.Buffer
 	for pid, p := range st.procs {
 		p.mu.Lock()
+		if agentID != "" && p.AgentID != agentID {
+			p.mu.Unlock()
+			continue
+		}
 		var state string
 		if p.Exited {
 			state = fmt.Sprintf("exited (%d)", p.ExitCode)

cmd/toolsrv/internal/server/server.go

@@ -177,10 +177,11 @@ func Spec(srv *Server) virtfs.FsNodeDecl {
 			),
 		),
 		virtfs.DirNode("proc",
-			virtfs.FileNode("list", 0444,
-				virtfs.Doc("List all processes: pid, state (running/exited (code)), tool"),
-				virtfs.Read(func() ([]byte, error) {
-					return []byte(srv.Fs.ListProcsWithState()), nil
+			virtfs.FileNode("list", 0666,
+				virtfs.Doc("List processes: write agent ID (or empty for all), read pid\\tstate\\ttool"),
+				virtfs.Request(func(_ context.Context, data []byte) ([]byte, error) {
+					agentID := strings.TrimSpace(string(data))
+					return []byte(srv.Fs.ListProcsForAgent(agentID)), nil
 				}),
 			),
 			virtfs.FileNode("new", 0666,