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.

instructions.md

@@ -14,21 +14,26 @@ interface below; there is nothing else to install or configure on a player's sid
 
 ## Getting set up
 
-1. Open this service's **Multiplayer Table** interface.
-2. Run the **Get Join Secret** action from this service's Actions menu, and copy the value it
+1. Run the **Get Join Secret** action from this service's Actions menu, and copy the value it
    returns.
-3. Share that secret, and the address you opened the interface at, with everyone you want to
-   play with. Anyone holding the secret can create a new game or join one that hasn't started yet.
-4. In the browser, click **Multiplayer**, then **Create Game** (or **Join Game** with a game code
-   someone else created), and enter the join secret when asked.
+2. Share that secret, and this service's address, with everyone you want to play with. Anyone
+   holding the secret can create a new game or join one that hasn't started yet.
+3. Open this service's **Multiplayer Table** interface. You'll land on the front page, which
+   offers three ways in: solitaire, the replay viewer, and multiplayer.
+4. Click **Play multiplayer**, then **Create Game** (or **Join Game** with a game code someone
+   else created), and enter the join secret when asked.
 
 ## Using Station Master
 
 ### Multiplayer Table
 
-Create or join a game, seat players (including filling empty seats with a bot), and start. Once a
-game is underway, this same interface is where every player plays their turns and watches the
-table — there is nothing else to open.
+The front page offers solitaire, the replay viewer, and multiplayer. **Play multiplayer** takes you
+to the lobby: create or join a game, seat players (including filling empty seats with a bot), and
+start. Once a game is underway, this same interface is where every player plays their turns and
+watches the table — there is nothing else to open.
+
+Solitaire runs entirely in your own browser and needs nothing from the server, so it works here
+exactly as it does on the public Station Master site.
 
 ### Get Join Secret