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/sheet-physics.test.ts

@@ -0,0 +1,48 @@
+import { describe, expect, it } from "vitest";
+import { nearestSnap, project, rubberband } from "../src/lib/sheet-physics";
+
+describe("project", () => {
+  it("零速度零位移", () => {
+    expect(project(0)).toBe(0);
+  });
+
+  it("符合指数衰减投影公式（1000px/s @ 0.998 ≈ 499px）", () => {
+    expect(project(1000, 0.998)).toBeCloseTo(499, 0);
+    expect(project(-1000, 0.998)).toBeCloseTo(-499, 0);
+  });
+
+  it("减速率越低，投影越短（0.99 比 0.998 更快停下）", () => {
+    expect(Math.abs(project(1000, 0.99))).toBeLessThan(Math.abs(project(1000, 0.998)));
+  });
+});
+
+describe("rubberband", () => {
+  it("越界越多显示越多，但增量递减（渐进阻尼）", () => {
+    const d = 800;
+    const r50 = rubberband(50, d);
+    const r100 = rubberband(100, d);
+    const r150 = rubberband(150, d);
+    expect(r100).toBeGreaterThan(r50);
+    expect(r150).toBeGreaterThan(r100);
+    expect(r100 - r50).toBeGreaterThan(r150 - r100);
+  });
+
+  it("显示越界量恒小于实际越界量", () => {
+    expect(rubberband(100, 800)).toBeLessThan(100);
+    expect(rubberband(1, 800)).toBeLessThan(1);
+  });
+});
+
+describe("nearestSnap", () => {
+  it("就近吸附", () => {
+    const snaps = [0, 300, 800] as const;
+    expect(nearestSnap(120, snaps)).toBe(0);
+    expect(nearestSnap(180, snaps)).toBe(300);
+    expect(nearestSnap(540, snaps)).toBe(300);
+    expect(nearestSnap(700, snaps)).toBe(800);
+  });
+
+  it("恰在中点时取先出现的候选", () => {
+    expect(nearestSnap(150, [0, 300])).toBe(0);
+  });
+});