Initialize repository with harness code and assets

Initial import of all source code, config, and README assets: the
packages workspace (cli, core, server, web, docs, landing, skills),
build scripts, tooling config, and CI workflows.

Includes the data-layout revision made on this branch: the local data
root defaults to ~/.penguin/data (PENGUIN_HOME still overrides; the
installer keeps its binaries in ~/.penguin), and every Agent lives
under <project>/agents/<agent>/ — path helpers, the three
agent-enumeration scans, the system prompt, built-in Skills, tests
and docs all follow the new layout.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_018ihk8iQuo3kv2aPjAYEPuR

packages/web/test/stream-follow.test.ts

@@ -0,0 +1,78 @@
+/**
+ * Unit tests for stream-follow.ts (issue #75): in a short scroll area (scrollable
+ * slack < 80px), scrolling up immediately exits auto-stick-to-bottom; staying at
+ * a historical position, streaming increments don't override that intent; the
+ * user can scroll back down to resume; content-shrink clamping isn't
+ * misread as an upward scroll.
+ */
+import { describe, expect, it } from "vitest";
+import { createStreamFollow } from "../src/features/chat/stream-follow";
+
+/** Short scroll area: content 500px, viewport 460px, scrollable slack only 40px (always under the 80px threshold). */
+const SHORT = { scrollHeight: 500, clientHeight: 460 };
+
+describe("createStreamFollow", () => {
+  it("短滚动区：wheel 上滚立即退出跟随，即使已在顶部（位置不再变化）", () => {
+    const f = createStreamFollow();
+    expect(f.stick).toBe(true);
+    f.scrolled({ ...SHORT, scrollTop: 40 }); // scroll event from the program sticking to bottom: still following.
+    expect(f.stick).toBe(true);
+    f.wheel(-3);
+    expect(f.stick).toBe(false);
+  });
+
+  it("短滚动区：滚动条/键盘上移（scrollTop 回退）同样退出", () => {
+    const f = createStreamFollow();
+    f.scrolled({ ...SHORT, scrollTop: 40 });
+    f.scrolled({ ...SHORT, scrollTop: 20 }); // moved up, 20px from bottom (> the 1px clamp margin).
+    expect(f.stick).toBe(false);
+  });
+
+  it("触摸下拉（手指向下移动）退出；上推不退出", () => {
+    const f = createStreamFollow();
+    f.touchStart(100);
+    f.touchMove(90); // finger pushes up = content scrolls down, stays following.
+    expect(f.stick).toBe(true);
+    f.touchMove(120); // finger pulls down = content scrolls up, exits.
+    expect(f.stick).toBe(false);
+    f.touchEnd();
+  });
+
+  it("停留历史位置时，流式增量（scrollTop 不动、内容变高）不改变意图", () => {
+    const f = createStreamFollow();
+    f.scrolled({ ...SHORT, scrollTop: 40 });
+    f.wheel(-3);
+    f.scrolled({ ...SHORT, scrollTop: 0 }); // scrolled up to the top.
+    expect(f.stick).toBe(false);
+    // Content keeps growing while the user's position stays put: as long as scrollTop
+    // doesn't change, following isn't mistakenly resumed.
+    f.scrolled({ scrollHeight: 900, clientHeight: 460, scrollTop: 0 });
+    expect(f.stick).toBe(false);
+  });
+
+  it("用户主动滚回底部附近（80px 内）恢复跟随", () => {
+    const f = createStreamFollow();
+    f.scrolled({ scrollHeight: 2000, clientHeight: 460, scrollTop: 1540 });
+    f.scrolled({ scrollHeight: 2000, clientHeight: 460, scrollTop: 800 }); // dragged up, exits.
+    expect(f.stick).toBe(false);
+    f.scrolled({ scrollHeight: 2000, clientHeight: 460, scrollTop: 1470 }); // back to 70px from bottom.
+    expect(f.stick).toBe(true);
+  });
+
+  it("内容收缩把 scrollTop 向下钳位（仍贴底）不算上滑", () => {
+    const f = createStreamFollow();
+    f.scrolled({ scrollHeight: 2000, clientHeight: 460, scrollTop: 1540 }); // stuck to bottom, following.
+    // Group collapse shrinks content height; the browser clamps scrollTop to the new
+    // bottom: it moved up, but it's still 0px from the bottom.
+    f.scrolled({ scrollHeight: 1500, clientHeight: 460, scrollTop: 1040 });
+    expect(f.stick).toBe(true);
+  });
+
+  it("首个滚动事件即处于历史位置（离底 ≥ 80px）：按位置初始化为不跟随", () => {
+    const f = createStreamFollow();
+    // The first event has no direction to judge from (e.g. a restored scroll position),
+    // and is 540px from the bottom: it shouldn't wait for a subsequent scroll-up to exit.
+    f.scrolled({ scrollHeight: 2000, clientHeight: 460, scrollTop: 1000 });
+    expect(f.stick).toBe(false);
+  });
+});