feat(changelog): lead each release with highlights and fold the rest away

A release entry now opens with a short list of highlights above its first
section. The What's new sheet, the website changelog and the GitHub release
body show those and keep the sections, the full record, behind one control,
so a 100-bullet release reads as ten lines.

CHANGELOG.md stays plain Markdown because the app and the website render it
without HTML, including apps already installed. Each surface folds the
sections itself; only the release body gets a <details> block, written by
Release Notes Sync. A release with nothing before its first section shows
its sections as before.

Adds the 0.16.0-beta.1 entry in the new format, with its Chinese
translation, and the highlight writing rules in docs/release.md.

scripts/sync-fdroid-changelogs.test.mjs

@@ -275,6 +275,28 @@ test("preserves the standalone 0.1.96 Android notice", () => {
   assert.equal(contents.includes("_This release"), false);
 });
 
+test("leads with an entry's highlights and spends the budget on them first", () => {
+  const highlight = (name) =>
+    `- **${name}:** ${"A highlight a user would name first. ".repeat(4).trim()} ([#1](https://github.com/getpaseo/paseo/pull/1))`;
+  const contents = formatFdroidChangelog(
+    [
+      highlight("First"),
+      highlight("Second"),
+      highlight("Third"),
+      "",
+      "### Fixed",
+      "",
+      "- Fixed a crash",
+    ],
+    { limit: CHANGELOG_CHARACTER_LIMIT },
+  );
+
+  assert.match(contents, /^- First: A highlight a user would name first\./);
+  assert.match(contents, /\n- Second: /);
+  assert.equal(contents.includes("Fixed a crash"), false);
+  assert.ok(contents.length <= CHANGELOG_CHARACTER_LIMIT);
+});
+
 test("--check fails when the generated files are missing or stale", () => {
   const changelog = "## 0.2.3 - 2026-07-27\n\n### Fixed\n\n- Something broke.\n";
   withTempRepo(