feat(initial): scaffold @push.rocks/smartchat with core, CLI, and web layers

Three-layer architecture built on @push.rocks/smartagent:
- ts/ — ChatSession wrapping runAgent() with conversation state management
- ts_cli/ — ink-based terminal chat TUI (React.createElement, no JSX)
- ts_web/ — Lit web components (smartchat-window, smartchat-message, smartchat-input)

ts_cli/smartchat.startchat.ts

@@ -0,0 +1,34 @@
+import { React, h, render } from './plugins.js';
+import type { LanguageModelV3, ToolSet } from './plugins.js';
+import { ChatApp } from './components.chatapp.js';
+
+export interface IStartChatOptions {
+  /** The language model to use */
+  model: LanguageModelV3;
+  /** System prompt for the agent */
+  system?: string;
+  /** Tools available to the agent */
+  tools?: ToolSet;
+  /** Maximum agentic steps per turn */
+  maxSteps?: number;
+  /** Display name for the model (shown in header/status) */
+  modelName?: string;
+}
+
+/**
+ * Start an interactive chat TUI in the terminal.
+ * Returns a promise that resolves when the user exits.
+ */
+export async function startChat(options: IStartChatOptions): Promise<void> {
+  const instance = render(
+    h(ChatApp, {
+      model: options.model,
+      system: options.system,
+      tools: options.tools,
+      maxSteps: options.maxSteps,
+      modelName: options.modelName,
+    }),
+  );
+
+  await instance.waitUntilExit();
+}