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_web/smartchat-window.ts

@@ -0,0 +1,179 @@
+import { LitElement, html, css } from './plugins.js';
+import type { CSSResult, TemplateResult, ChatSession, IAgentRunResult } from './plugins.js';
+import './smartchat-message.js';
+import './smartchat-input.js';
+
+interface IDisplayMessage {
+  role: 'user' | 'assistant' | 'tool';
+  content: string;
+  toolName?: string;
+}
+
+export class SmartchatWindow extends LitElement {
+  declare chatSession: ChatSession;
+  declare placeholder: string;
+  private messages: IDisplayMessage[] = [];
+  private busy = false;
+  private streamingText = '';
+
+  static properties = {
+    chatSession: { attribute: false },
+    placeholder: { type: String },
+  };
+
+  static styles: CSSResult = css`
+    :host {
+      display: flex;
+      flex-direction: column;
+      height: 100%;
+      background: var(--smartchat-bg, #111827);
+      color: var(--smartchat-text, #e5e7eb);
+      font-family: var(--smartchat-font, system-ui, -apple-system, sans-serif);
+      border-radius: var(--smartchat-radius, 12px);
+      overflow: hidden;
+    }
+
+    .message-list {
+      flex: 1;
+      overflow-y: auto;
+      padding: 16px;
+      display: flex;
+      flex-direction: column;
+      gap: 4px;
+    }
+
+    .empty-state {
+      display: flex;
+      align-items: center;
+      justify-content: center;
+      flex: 1;
+      color: var(--smartchat-muted, #6b7280);
+      font-size: 14px;
+    }
+
+    .streaming {
+      padding: 8px 12px;
+      background: var(--smartchat-assistant-bubble, #374151);
+      color: var(--smartchat-assistant-text, #e5e7eb);
+      border-radius: 8px;
+      border-bottom-left-radius: 2px;
+      max-width: 85%;
+      white-space: pre-wrap;
+    }
+
+    .cursor {
+      display: inline-block;
+      width: 2px;
+      height: 1em;
+      background: var(--smartchat-cursor, #6366f1);
+      animation: blink 1s step-end infinite;
+      vertical-align: text-bottom;
+    }
+
+    @keyframes blink {
+      50% { opacity: 0; }
+    }
+
+    .input-area {
+      padding: 12px 16px;
+      border-top: 1px solid var(--smartchat-border, #1f2937);
+    }
+  `;
+
+  constructor() {
+    super();
+    this.placeholder = 'Type a message...';
+  }
+
+  connectedCallback() {
+    super.connectedCallback();
+    if (this.chatSession) {
+      this.chatSession.updateCallbacks({
+        onToken: (delta: string) => {
+          this.streamingText += delta;
+          this.requestUpdate();
+          this.scrollToBottom();
+        },
+        onToolCall: (name: string) => {
+          this.messages = [
+            ...this.messages,
+            { role: 'tool', content: '', toolName: name },
+          ];
+          this.requestUpdate();
+          this.scrollToBottom();
+        },
+      });
+    }
+  }
+
+  private scrollToBottom() {
+    requestAnimationFrame(() => {
+      const list = this.shadowRoot?.querySelector('.message-list');
+      if (list) {
+        list.scrollTop = list.scrollHeight;
+      }
+    });
+  }
+
+  private async handleSend(e: CustomEvent<{ text: string }>) {
+    if (this.busy) return;
+
+    const text = e.detail.text;
+    this.messages = [...this.messages, { role: 'user', content: text }];
+    this.busy = true;
+    this.streamingText = '';
+    this.requestUpdate();
+    this.scrollToBottom();
+
+    try {
+      const result = await this.chatSession.send(text);
+      this.streamingText = '';
+      this.messages = [...this.messages, { role: 'assistant', content: result.text }];
+    } catch (error) {
+      const errMsg = error instanceof Error ? error.message : String(error);
+      this.messages = [
+        ...this.messages,
+        { role: 'assistant', content: `Error: ${errMsg}` },
+      ];
+    } finally {
+      this.busy = false;
+      this.requestUpdate();
+      this.scrollToBottom();
+    }
+  }
+
+  render(): TemplateResult {
+    return html`
+      <div class="message-list">
+        ${this.messages.length === 0 && !this.busy
+          ? html`<div class="empty-state">Start a conversation...</div>`
+          : ''}
+        ${this.messages.map(
+          (msg) => html`
+            <smartchat-message
+              role=${msg.role}
+              content=${msg.content}
+              .toolName=${msg.toolName ?? ''}
+            ></smartchat-message>
+          `,
+        )}
+        ${this.busy && this.streamingText
+          ? html`
+              <div class="streaming">
+                ${this.streamingText}<span class="cursor"></span>
+              </div>
+            `
+          : ''}
+      </div>
+      <div class="input-area">
+        <smartchat-input
+          ?disabled=${this.busy}
+          placeholder=${this.placeholder}
+          @send=${this.handleSend}
+        ></smartchat-input>
+      </div>
+    `;
+  }
+}
+
+customElements.define('smartchat-window', SmartchatWindow);