fix: return fetched content to LLM in web_fetch tool (#833)

* fix: return fetched content to LLM in web_fetch tool

WebFetchTool.Execute was setting ForLLM to a summary string
("Fetched N bytes from URL ...") instead of the actual extracted
text. This meant the LLM never saw the page content and could not
answer questions based on fetched web pages.

Return the extracted text in ForLLM so the model can use it.

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

* fix: put full JSON result in ForLLM, summary in ForUser

Accept suggestion from afjcjsbx: the LLM should receive the full JSON
result (including extracted text) while the user sees a short summary.
Update tests to match the new field assignment.

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

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

pkg/tools/web.go

@@ -661,14 +661,14 @@ func (t *WebFetchTool) Execute(ctx context.Context, args map[string]any) *ToolRe
 	resultJSON, _ := json.MarshalIndent(result, "", "  ")
 
 	return &ToolResult{
-		ForLLM: fmt.Sprintf(
+		ForLLM: string(resultJSON),
+		ForUser: fmt.Sprintf(
 			"Fetched %d bytes from %s (extractor: %s, truncated: %v)",
 			len(text),
 			urlStr,
 			extractor,
 			truncated,
 		),
-		ForUser: string(resultJSON),
 	}
 }