feat(v2): chat command history + smart auto-scroll

Command history:
- Up/Down arrow keys browse sent command history (like bash/console)
- 50 commands stored per character in localStorage
- Persists across page reloads and browser sessions
- Current input preserved when browsing (restored on Down past end)
- Duplicates kept (matches user preference)

Smart auto-scroll:
- New messages only auto-scroll if user is already at the bottom
- If user has scrolled up to read history, it stays put
- Sending a message snaps back to bottom
- 30px threshold for "at bottom" detection

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

static/index.html

@@ -8,7 +8,7 @@
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     <link rel="preload" as="fetch" href="/dungeon_tiles.json" crossorigin="anonymous" />
-    <script type="module" crossorigin src="/assets/index-BNR09N5o.js"></script>
+    <script type="module" crossorigin src="/assets/index-BZJ3WwmC.js"></script>
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     <link rel="stylesheet" crossorigin href="/assets/index-DODaoLcJ.css">
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