refactor: notify/footer 持久配置收编到 config/，chrome bridge 地址固定

仓库规则要求 config/ 为唯一配置来源、不以环境变量作持久默认值：
- pi-notify 改读 config/pi-notify.json（逐字段校验回退，复用原 parsers 钳制）
- pi-minimal-footer 改读 config/pi-minimal-footer.json
- pi-chrome 移除 PI_CHROME_BRIDGE_HOST/PORT，固定 127.0.0.1:17318
  （浏览器端 service_worker.js 硬编码同一地址，单侧可配只会断连）

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pi-minimal-footer/test/settings.test.ts

@@ -0,0 +1,51 @@
+import assert from "node:assert/strict";
+import { mkdtempSync, rmSync, writeFileSync } from "node:fs";
+import { tmpdir } from "node:os";
+import { join } from "node:path";
+import { afterEach, describe, it } from "node:test";
+
+import { readFooterSettings } from "../settings.ts";
+
+let tempDir: string | undefined;
+
+afterEach(() => {
+  if (tempDir) {
+    rmSync(tempDir, { recursive: true, force: true });
+    tempDir = undefined;
+  }
+});
+
+function configPath(contents: string): string {
+  tempDir = mkdtempSync(join(tmpdir(), "pi-minimal-footer-settings-"));
+  const path = join(tempDir, "pi-minimal-footer.json");
+  writeFileSync(path, contents);
+  return path;
+}
+
+const expectedDefaults = { showCwd: true, showBranch: true };
+
+describe("readFooterSettings", () => {
+  it("returns all defaults when the config file is missing", () => {
+    assert.deepEqual(readFooterSettings("/does/not/exist/pi-minimal-footer.json"), expectedDefaults);
+  });
+
+  it("returns all defaults for malformed or non-object JSON", () => {
+    for (const contents of ["not json", "[1,2]", "42"]) {
+      assert.deepEqual(readFooterSettings(configPath(contents)), expectedDefaults, contents);
+    }
+  });
+
+  it("adopts explicit boolean values", () => {
+    assert.deepEqual(
+      readFooterSettings(configPath(JSON.stringify({ showCwd: false, showBranch: false }))),
+      { showCwd: false, showBranch: false },
+    );
+  });
+
+  it("falls back per-field for non-boolean values", () => {
+    assert.deepEqual(
+      readFooterSettings(configPath(JSON.stringify({ showCwd: "no", showBranch: 0 }))),
+      expectedDefaults,
+    );
+  });
+});