chore: import upstream snapshot with attribution

tests/unit/plugins-logger.test.ts

@@ -0,0 +1,44 @@
+import { describe, it, afterEach } from "node:test";
+import assert from "node:assert";
+import { existsSync, readFileSync, rmSync } from "fs";
+import { join } from "path";
+import { tmpdir } from "os";
+import { PluginLogger } from "../../src/lib/plugins/logger.ts";
+
+describe("PluginLogger", () => {
+  const testDir = join(tmpdir(), `plugin-logger-test-${Date.now()}`);
+
+  afterEach(() => {
+    try { rmSync(testDir, { recursive: true, force: true }); } catch {}
+  });
+
+  it("creates log file and writes JSON entries", () => {
+    const logger = new PluginLogger("test-plugin", testDir);
+    logger.info("hello world");
+    const logPath = join(testDir, "test-plugin", "plugin.log");
+    assert.ok(existsSync(logPath));
+    const content = readFileSync(logPath, "utf-8").trim();
+    const entry = JSON.parse(content);
+    assert.strictEqual(entry.level, "INFO");
+    assert.strictEqual(entry.message, "hello world");
+    assert.ok(entry.timestamp);
+  });
+
+  it("writes error entries", () => {
+    const logger = new PluginLogger("err-plugin", testDir);
+    logger.error("bad thing", { code: 500 });
+    const logPath = join(testDir, "err-plugin", "plugin.log");
+    const entry = JSON.parse(readFileSync(logPath, "utf-8").trim());
+    assert.strictEqual(entry.level, "ERROR");
+    assert.deepStrictEqual(entry.data, { code: 500 });
+  });
+
+  it("appends multiple entries", () => {
+    const logger = new PluginLogger("multi-plugin", testDir);
+    logger.info("first");
+    logger.warn("second");
+    const logPath = join(testDir, "multi-plugin", "plugin.log");
+    const lines = readFileSync(logPath, "utf-8").trim().split("\n");
+    assert.strictEqual(lines.length, 2);
+  });
+});