fix: add configureawait false to reduce deadlock risk in websearchtool

Added ConfigureAwait(false) to all await calls in SearchBingAsync and
SearchSerpAPIAsync methods to reduce deadlock risk when these async
methods are called synchronously via GetAwaiter().GetResult() in the
Execute method.

This follows async best practices for library code and mitigates issues
with blocking async continuations in synchronization contexts.

Fixes PR #423 comment #6.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

Author: ooples

src/Tools/WebSearchTool.cs

@@ -158,15 +158,15 @@ private async Task<string> SearchBingAsync(string query)
         var request = new HttpRequestMessage(HttpMethod.Get, url);
         request.Headers.Add("Ocp-Apim-Subscription-Key", _apiKey);
 
-        var response = await _httpClient.SendAsync(request);
+        var response = await _httpClient.SendAsync(request).ConfigureAwait(false);
 
         if (!response.IsSuccessStatusCode)
         {
-            var errorContent = await response.Content.ReadAsStringAsync();
+            var errorContent = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
             throw new HttpRequestException($"Bing Search API error ({response.StatusCode}): {errorContent}");
         }
 
-        var content = await response.Content.ReadAsStringAsync();
+        var content = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
         var searchResponse = JsonConvert.DeserializeObject<BingSearchResponse>(content);
 
         if (searchResponse?.WebPages?.Value == null || searchResponse.WebPages.Value.Length == 0)
@@ -184,15 +184,15 @@ private async Task<string> SearchSerpAPIAsync(string query)
     {
         var url = $"https://serpapi.com/search.json?q={Uri.EscapeDataString(query)}&num={_defaultResultCount}&api_key={_apiKey}&engine=google";
 
-        var response = await _httpClient.GetAsync(url);
+        var response = await _httpClient.GetAsync(url).ConfigureAwait(false);
 
         if (!response.IsSuccessStatusCode)
         {
-            var errorContent = await response.Content.ReadAsStringAsync();
+            var errorContent = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
             throw new HttpRequestException($"SerpAPI error ({response.StatusCode}): {errorContent}");
         }
 
-        var content = await response.Content.ReadAsStringAsync();
+        var content = await response.Content.ReadAsStringAsync().ConfigureAwait(false);
         var searchResponse = JsonConvert.DeserializeObject<SerpAPIResponse>(content);
 
         if (searchResponse?.OrganicResults == null || searchResponse.OrganicResults.Length == 0)