feat: integrate Pi backend and Pi Web

pi-web/lib/patch.test.mjs

@@ -0,0 +1,63 @@
+import assert from "node:assert/strict";
+import test from "node:test";
+
+async function loadSubject() {
+  return import("./patch.ts");
+}
+
+test("parses paired changes into split diff rows", async () => {
+  const { parseUnifiedPatch } = await loadSubject();
+  const files = parseUnifiedPatch(`--- a/demo.ts
++++ b/demo.ts
+@@ -10,3 +10,3 @@
+ const keep = true;
+-const value = "old";
++const value = "new";
+ done();
+`);
+
+  assert.equal(files?.length, 1);
+  assert.equal(files?.[0].oldPath, "a/demo.ts");
+  assert.equal(files?.[0].newPath, "b/demo.ts");
+  assert.deepEqual(files?.[0].rows.filter((row) => row.type === "line"), [
+    {
+      type: "line",
+      left: { lineNo: 10, text: "const keep = true;", type: "context" },
+      right: { lineNo: 10, text: "const keep = true;", type: "context" },
+    },
+    {
+      type: "line",
+      left: { lineNo: 11, text: 'const value = "old";', type: "removed" },
+      right: { lineNo: 11, text: 'const value = "new";', type: "added" },
+    },
+    {
+      type: "line",
+      left: { lineNo: 12, text: "done();", type: "context" },
+      right: { lineNo: 12, text: "done();", type: "context" },
+    },
+  ]);
+});
+
+test("pads one-sided additions and removes timestamp suffixes from file paths", async () => {
+  const { parseUnifiedPatch } = await loadSubject();
+  const files = parseUnifiedPatch(`--- a/demo.ts\t2026-01-01
++++ b/demo.ts\t2026-01-02
+@@ -1,1 +1,2 @@
+ first
++second
+`);
+
+  assert.equal(files?.[0].oldPath, "a/demo.ts");
+  assert.equal(files?.[0].newPath, "b/demo.ts");
+  assert.deepEqual(files?.[0].rows.at(-1), {
+    type: "line",
+    left: { lineNo: null, text: "", type: "empty" },
+    right: { lineNo: 2, text: "second", type: "added" },
+  });
+});
+
+test("returns null for text without diff lines", async () => {
+  const { parseUnifiedPatch } = await loadSubject();
+
+  assert.equal(parseUnifiedPatch("not a patch"), null);
+});