Give the download one permanent address

The manifest names the current artifact and the directory listing is off,
so "where do I download it by hand" could only be answered by reading the
manifest first. latest.apk is a symlink the release script repoints — git
stores it as a path, so it costs bytes rather than another 34MB a
release, and every past build stays reachable under its own name, which
is what lets a device midway through a download survive a release.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

README.md

@@ -22,6 +22,13 @@ the cheaper trade against standing up artifact storage for one app; if the
 repository ever gets uncomfortable, the history is disposable — only the
 newest artifact is ever fetched.
 
+## Downloading by hand
+
+`https://media-updates.petruzalekr.cz/latest.apk` always points at the newest
+build — a symlink the release script repoints, so the address never changes.
+Every past build stays reachable under its own `media-<build>.apk` name, which
+is what lets a device that is midway through a download survive a release.
+
 ## The manifest
 
 ```json

public/latest.apk

@@ -0,0 +1 @@
+media-6.apk

release.py

@@ -56,6 +56,14 @@ def main() -> None:
         json.dumps(manifest, indent=2, ensure_ascii=False) + "\n",
         encoding="utf-8")
 
+    # A stable name, so "where do I download it" has one permanent answer
+    # instead of one that has to be looked up in the manifest each time. A
+    # symlink rather than a copy: git stores it as a path, so it costs bytes
+    # rather than another 34MB per release.
+    latest = public / "latest.apk"
+    latest.unlink(missing_ok=True)
+    latest.symlink_to(name)
+
     subprocess.run(["git", "add", "-A"], cwd=HERE, check=True)
     subprocess.run(
         ["git", "commit", "-m", f"Release {version}+{build}"],