fix(agent): refresh outputFormat lookup on each turn

The OutputFormat function was set once at runtime build time and stored
in ag.runtime.OutputFormat. When tools were dynamically loaded via
tool_load, the tool definitions were refreshed but the OutputFormat
lookup still used the stale runtime version that didn't know about
newly loaded tools.

Build the outputFormats map from the fresh tool list on each turn,
just like we already do for the tool definitions. This ensures
outputFormat (e.g., 'diff' for file_edit) is available immediately
after loading a tool.

agent/turn.go

@@ -132,6 +132,18 @@ func (ag *Agent) executeTurn(ctx context.Context, input string) string {
 		return ""
 	}
 	tools := toolInfosToBackend(ti)
+
+	// Build output format lookup from the fresh tool list. This ensures
+	// dynamically loaded tools (via tool_load) have their outputFormat
+	// available immediately, not just after a full runtime rebuild.
+	outputFormats := make(map[string]string, len(ti))
+	for _, info := range ti {
+		outputFormats[info.Name] = info.OutputFormat
+	}
+	outputFormatFn := func(name string) string {
+		return outputFormats[name]
+	}
+
 	ag.cfg = agentConfig{
 		Backend:          ag.runtime.Backend,
 		preamble:         ag.runtime.Preamble,
@@ -139,7 +151,7 @@ func (ag *Agent) executeTurn(ctx context.Context, input string) string {
 		Tools:            tools,
 		Exec:             ag.runtime.Exec,
 		ClassifyTool:     ag.runtime.ClassifyTool,
-		OutputFormat:     ag.runtime.OutputFormat,
+		OutputFormat:     outputFormatFn,
 		ClassifyTier:     ag.runtime.ClassifyTier,
 		GenerationParams: ag.runtime.GenParams,
 		MaxSteps:         ag.runtime.MaxSteps,