Bundle Station Master v0.5.2, and fix the package version scheme

Submodule pin moves to v0.5.2, which carries the working splash-page
multiplayer door and the GET /api/health probe behind it.

The interface goes back to serving `/` — the splash, which is the front
door to all three ways to play. It pointed at /play.html only because the
splash's multiplayer door was hardcoded to "Coming soon", making the front
page a dead end on a real server; v0.5.2 removes the reason for the
workaround. The splash now probes /api/health on load, so served from here
it opens the lobby and served as a plain static site it says plainly that
it needs a server.

The package version was wrong and is corrected: 1.0.0:0 -> 0.5.2:0. That
1.0.0 was the scaffold's placeholder, left in by mistake — versions.md's
consistency checklist requires the upstream half to match the bundled tag,
which is what makes "bump the pin, bump the version" one mechanical action
rather than a judgement call. No historical version file is needed: the
placeholder carried no migration and was never published anywhere.

The correction is a downgrade in ExVer terms, so StartOS refused to install
over the existing copy ("uninit target range `!` is unsatisfiable"). The
installed package was therefore removed and reinstalled — checked first
that the volume held only an auto-generated join secret and no games. Two
consequences, both one-time and both recorded in UPDATING.md: the join
secret is regenerated, and the host's public domain binding was dropped
with the uninstall and has to be re-added.

Verified on phoenix.local: builds as v0.5.2:0, installs, starts, and serves
/api/health 200 with the right body; the splash carries all three doors
including a live ./play.html?lobby, no "Coming soon" anywhere, all three
ids the probe addresses present, and #lobby rendering on play.html?lobby.

startos/interfaces.ts

@@ -18,12 +18,12 @@ export const setInterfaces = sdk.setupInterfaces(async ({ effects }) => {
     masked: false,
     schemeOverride: null,
     username: null,
-    // `/` serves index.html — the game's marketing splash, identical to the public static
-    // solitaire site and with no lobby or Multiplayer button on it (both live on play.html; see
-    // src/web/main.ts's `start()` and the door link in index.html). That page makes sense for a
-    // stranger landing on the public site, not for someone who just installed a dedicated
-    // multiplayer server — so this interface opens straight at the game screen instead.
-    path: '/play.html',
+    // The splash at `/`, which is the front door to all three ways to play: solitaire, the
+    // replay viewer, and multiplayer. Its multiplayer door probes `/api/health` on load, so
+    // served from here it opens the lobby, and served as a plain static site it says plainly
+    // that it needs a server. This briefly pointed at `/play.html` instead, back when that door
+    // was hardcoded to "Coming soon" and the splash was a dead end on a real server.
+    path: '',
     query: {},
   })