feat: add extraction schema, sidebar nav, few-shot prompting, and prompt settings

Overhaul extraction pipeline with new TradeItem model, conversation flow,
and dedicated extraction endpoint. Add sidebar navigation with NavMenu
component and landing page. Introduce few-shot prompting service and
tests. Add prompt settings and email upload specs. Update OpenSpec
tooling with improved export-spec and extract-feature commands. Archive
completed changes and export full specs.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/ChatAgent.Api/Program.cs

@@ -53,10 +53,50 @@ builder.Services.AddOpenAIChatCompletion(
 // any AI services (like the chat completion above) that are already registered.
 builder.Services.AddKernel();
 
-// Register the ExtractionPlugin so the Kernel can expose its [KernelFunction] methods
-// as tools. When the LLM sees these tools, it can decide to call them during a conversation
-// to validate extracted data. The plugin is registered as a singleton via DI.
-builder.Services.AddSingleton<ChatAgent.Api.Plugins.ExtractionPlugin>();
+// --- External API Typed HttpClients ---
+//
+// Each extraction tool wraps an external API call. We register typed HttpClients
+// so that each service gets its own HttpClient with a pre-configured base URL.
+// AddHttpClient<T>() uses IHttpClientFactory under the hood, which manages
+// HttpClient lifetimes and avoids socket exhaustion.
+
+builder.Services.AddHttpClient<ChatAgent.Api.Services.CounterpartyApiClient>(client =>
+{
+    client.BaseAddress = new Uri(
+        builder.Configuration["ExternalApis:CounterpartyBaseUrl"] ?? "http://localhost:5000/api/counterparty");
+});
+
+builder.Services.AddHttpClient<ChatAgent.Api.Services.TradeApiClient>(client =>
+{
+    client.BaseAddress = new Uri(
+        builder.Configuration["ExternalApis:TradeBaseUrl"] ?? "http://localhost:5000/api/trade");
+});
+
+builder.Services.AddHttpClient<ChatAgent.Api.Services.CurrencyApiClient>(client =>
+{
+    client.BaseAddress = new Uri(
+        builder.Configuration["ExternalApis:CurrencyBaseUrl"] ?? "http://localhost:5000/api/currency");
+});
+
+// --- Few-Shot Prompting Service ---
+//
+// FewShotService loads the extraction instruction template and few-shot examples
+// from disk at startup. It pre-assembles a ChatHistory prefix that is cloned
+// for each extraction request. Registered as a singleton since examples don't
+// change at runtime.
+// Resolve the examples path relative to the content root so it works correctly
+// both when running the app normally and in WebApplicationFactory test contexts.
+var examplesRelativePath = builder.Configuration["Examples:FewShotPath"] ?? "examples/extraction";
+var examplesAbsolutePath = Path.IsPathRooted(examplesRelativePath)
+    ? examplesRelativePath
+    : Path.Combine(builder.Environment.ContentRootPath, examplesRelativePath);
+builder.Services.AddSingleton(new ChatAgent.Api.Services.FewShotService(examplesAbsolutePath));
+
+// Register the ExtractionPlugin with its typed HttpClient dependencies.
+// The plugin exposes [KernelFunction] methods as tools the LLM can call
+// to look up counterparties, validate trades, currencies, and the extraction schema.
+// Scoped lifetime because it depends on typed HttpClients (which are transient).
+builder.Services.AddScoped<ChatAgent.Api.Plugins.ExtractionPlugin>();
 
 // AddCors() registers Cross-Origin Resource Sharing services.
 // CORS is REQUIRED because the Blazor WASM client runs on a different origin