feat: make tool_load a built-in tool

tool_load must be handled specially by the agent runtime because tools
run inside toolsrv's sandbox and cannot load other tools into
themselves. The runtime now intercepts tool_load calls and directly
invokes ToolServer.LoadTool().

This is the only built-in tool - all others are external scripts.

cmd/olliesrv/internal/agent/loop.go

@@ -482,6 +482,31 @@ func execOne(rt *Runtime, ctx TurnCtx, call backend.ToolCall, resultCache *sync.
 	var resultBlocks []backend.ContentBlock
 	var isErr bool
 
+	// Built-in: tool_load - must be handled specially because tools run inside
+	// toolsrv and can't load other tools into themselves.
+	if call.Name == "tool_load" {
+		var args struct {
+			Name string `json:"name"`
+		}
+		if err := json.Unmarshal(call.Arguments, &args); err != nil {
+			result = "error: " + err.Error()
+			isErr = true
+		} else if args.Name == "" {
+			result = "error: name is required"
+			isErr = true
+		} else if rt.ToolServer == nil {
+			result = "error: no tool server"
+			isErr = true
+		} else if err := rt.ToolServer.LoadTool(args.Name); err != nil {
+			result = "error: " + err.Error()
+			isErr = true
+		} else {
+			result = "loaded: " + args.Name
+		}
+		emit(ctx, Event{Role: "tool", Name: call.Name, Content: result, OutputFormat: toolOutputFormat(rt, call.Name)})
+		return toolResult{ToolCallID: call.ID, Name: call.Name, Content: result, IsError: isErr}, false
+	}
+
 	if rt.Exec != nil {
 		out, blocks, err := rt.Exec(ctx, call.Name, call.Arguments)
 		if err != nil {

data/tools/tool_load

@@ -3,8 +3,7 @@
 # ollie:prompt
 # ## tool_load
 #
-# Load a tool into the current session/agent by writing its name to
-# `session/{sid}/agent/{aid}/tools` via ollie-9p.
+# Load a tool into the current session/agent.
 #
 # **Args**: `name` (required) — the tool name to load.
 #
@@ -15,6 +14,7 @@
 
 set -euo pipefail
 
+# This tool just outputs the name - the actual loading is handled by
+# the agent framework when it receives the tool result.
 name=$(grep -oP '"name"\s*:\s*"\K[^"]+')
-echo "$name" | ollie-9p write "session/$OLLIE_SESSION_ID/agent/$OLLIE_UNAME/tools"
-echo "loaded: $name"
+echo "STATUS=ok TOOL_LOAD=$name"