feat: inline prompt history area — scrollable session messages

The inline prompt now shows the current session's full message
history (user + assistant), scrollable, replacing the single-output
display from the previous commit. The user can scroll back through
prior exchanges in the same notebook's OpenCode session.

Server (opencode_bridge/):
  - New route: GET /opencode-bridge/session-messages?notebook=<path>
    - Resolves notebook to session via SessionManager.peek (no create).
    - If no session: {"messages": []} (no OpenCode call).
    - Else: GET /session/{id}/message on OpenCode Serve, project the
      raw {info, parts}[] into a frontend-friendly {role, content}[].
  - OpenCodeClient.list_session_messages(sid).
  - SessionManager.peek(notebook_path) -> Optional[str] (read without
    creating, to avoid spawning a session just to report emptiness).
  - Wired the new route in setup_route_handlers.

Client (src/):
  - types.ts: OpenCodeMessage { role, content } + OpenCodeMessagesResponse.
  - api/opencode_client.ts: callOpenCodeSessionMessages(notebook, serverSettings).
  - components/opencode_inline_prompt.ts:
    - Replaces the single .opencode-inline-output area with a
      scrollable .opencode-inline-history (max-height 320px, overflow-y
      auto, auto-scrolls to bottom on update).
    - setMessages(messages): renders user messages as plain text,
      assistant messages via marked.parse. No more setOutput/hideOutput.
  - components/opencode_cell_actions.ts:
    - _showPrompt now fires a _refreshHistory(notebookPath) which
      fetches and calls prompt.setMessages.
    - _handleResponse on success also calls _refreshHistory (the new
      assistant message appears as the last item in the history).
    - Cell source is still NOT replaced.
  - api/opencode_client module is mocked in the cell_actions test to
    avoid jsdom network calls.

style/base.css:
  - .opencode-inline-output* rules replaced with .opencode-inline-history
    (max-height 320px, overflow-y auto, border, padding) and
    .opencode-msg / .opencode-msg-user / .opencode-msg-assistant.
  - pre/code/p/h1-3 content styling scoped under .opencode-inline-history.

Tests:
  - pytest 37/37: FakeOpenCodeClient.list_session_messages + 3 new
    session_messages route tests (no session, projects messages, 400).
  - jest 29/29: setMessages renders user/assistant + history area tests.
  - FakeSessionManager.peek (returns None when session_id is falsy).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/components/opencode_inline_prompt.ts

@@ -1,17 +1,19 @@
 /**
  * Inline prompt widget attached to a cell's DOM when the AI button is clicked.
- * Renders two <select> boxes (provider + model), a textarea, and send/cancel
- * buttons. The model select's default for the chosen provider is
- * `default[providerID]` (from the /config/providers response) when that
- * modelID is present in the provider's models; otherwise the first model.
+ * Renders two <select> boxes (provider + model), a textarea, send/cancel
+ * buttons, and a scrollable history area that shows the current session's
+ * messages (user + assistant). The model select's default for the chosen
+ * provider is `default[providerID]` from the /config/providers response.
  *
- * v3-final: no settings — picks come from the OpenCode Serve providers cache.
+ * v3-final: no settings — picks come from the OpenCode Serve providers
+ * cache; history comes from /session-messages; cell source is NOT replaced
+ * (the AI reply is rendered as markdown inside this history area).
  */
 import { CodeCell } from '@jupyterlab/cells';
 import { Widget } from '@lumino/widgets';
 import { marked } from 'marked';
 
-import type { OpenCodeProvidersResponse } from '../types';
+import type { OpenCodeMessage, OpenCodeProvidersResponse } from '../types';
 
 export interface IOpenCodeInlinePromptOptions {
   onSubmit: (text: string, providerId?: string, modelId?: string) => void;
@@ -70,8 +72,7 @@ export class OpenCodeInlinePrompt extends Widget {
   private _modelSelect: HTMLSelectElement | null = null;
   private _providerModels: FlatProvider[];
   private _defaultMap: { [pid: string]: string };
-  private _outputArea: HTMLDivElement;
-  private _outputContent: HTMLDivElement;
+  private _historyEl: HTMLDivElement;
 
   constructor(
     _cell: CodeCell,
@@ -154,33 +155,15 @@ export class OpenCodeInlinePrompt extends Widget {
       }
       this.node.appendChild(row);
     }
+
+    // Scrollable history of the current session's messages. Empty until
+    // setMessages() is called by the owning cell action.
+    this._historyEl = document.createElement('div');
+    this._historyEl.className = 'opencode-inline-history';
+    this.node.appendChild(this._historyEl);
+
     this.node.appendChild(this._textarea);
     this.node.appendChild(actions);
-
-    // Output area: hidden by default; revealed by setOutput() with the
-    // markdown-rendered AI response. The cell source is NOT replaced.
-    this._outputArea = document.createElement('div');
-    this._outputArea.className = 'opencode-inline-output';
-    this._outputArea.style.display = 'none';
-    const outputHeader = document.createElement('div');
-    outputHeader.className = 'opencode-inline-output-header';
-    const outputTitle = document.createElement('span');
-    outputTitle.textContent = '结果';
-    const outputCloseBtn = document.createElement('button');
-    outputCloseBtn.className = 'opencode-inline-output-close';
-    outputCloseBtn.type = 'button';
-    outputCloseBtn.textContent = '✕';
-    outputCloseBtn.title = '关闭输出';
-    outputCloseBtn.addEventListener('click', () => {
-      this.hideOutput();
-    });
-    outputHeader.appendChild(outputTitle);
-    outputHeader.appendChild(outputCloseBtn);
-    this._outputContent = document.createElement('div');
-    this._outputContent.className = 'opencode-inline-output-content';
-    this._outputArea.appendChild(outputHeader);
-    this._outputArea.appendChild(this._outputContent);
-    this.node.appendChild(this._outputArea);
   }
 
   private _rebuildModelSelect(providerId: string | undefined): void {
@@ -226,18 +209,23 @@ export class OpenCodeInlinePrompt extends Widget {
   }
 
   /**
-   * Render the AI response as markdown and show the output area in place
-   * of replacing the cell source. Safe for local-trusted content from the
-   * user's OpenCode Serve; do not feed untrusted markdown here without
-   * adding a sanitizer (e.g. DOMPurify).
+   * Render the current session's messages into the scrollable history
+   * area. User messages are plain text; assistant messages are rendered
+   * as markdown via marked. Auto-scrolls to the bottom so the most
+   * recent message is visible.
    */
-  setOutput(markdown: string): void {
-    this._outputContent.innerHTML = marked.parse(markdown) as string;
-    this._outputArea.style.display = 'block';
-  }
-
-  hideOutput(): void {
-    this._outputArea.style.display = 'none';
-    this._outputContent.textContent = '';
+  setMessages(messages: OpenCodeMessage[]): void {
+    this._historyEl.textContent = '';
+    for (const msg of messages) {
+      const wrap = document.createElement('div');
+      wrap.className = `opencode-msg opencode-msg-${msg.role}`;
+      if (msg.role === 'user') {
+        wrap.textContent = msg.content;
+      } else {
+        wrap.innerHTML = marked.parse(msg.content) as string;
+      }
+      this._historyEl.appendChild(wrap);
+    }
+    this._historyEl.scrollTop = this._historyEl.scrollHeight;
   }
 }