Share a turn with the world: /watch links, cards and chrome included

The share button lands on the instant replay. One click mints a slug —
persistent, unguessable, one per (room, turn) — and copies a /watch
link anyone can open: the server rebuilds exactly that turn for the
nameless SPECTATOR, public knowledge only, none of the rest of the
game visible. The page arrives with its OpenGraph card pre-baked into
the head (crawlers never run the app): the turn's title and round in
the text, and an og.png of the maze itself — cells, walls, doors, warp
mouths, homes, standees — painted server-side and PNG-encoded with
nothing but node's own zlib. The viewer page wears its chrome: the
WIZ-WAR masthead linking home, the turn's title, the reel opening
straight into the turn-owner's eyes with a "watch it again" loop, and
a footer that says what this table is and deals the visitor in.

The share page loads as its own entry so a shared link never drags the
full app's socket appetite along; the reel's modal scrim learns to
stand in a page instead of over one.

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

packages/web/src/App.svelte

@@ -1612,7 +1612,7 @@
   {/if}
 
   {#if net.moment && net.moment.length > 0}
-    <Replay steps={net.moment} moment onclose={() => net.closeMoment()} />
+    <Replay steps={net.moment} moment onshare={() => net.requestShare()} onclose={() => net.closeMoment()} />
   {:else if net.catchUp && net.catchUp.length > 0}
     <Replay steps={net.catchUp} onclose={() => net.closeCatchUp()} />
   {:else if local.replaySteps && local.replaySteps.length > 0}