chore(quota): drop the Command Code usage provider

Command Code's official API has no usage endpoints; the old usage source
was the unofficial studio API reached through a now-archived plugin, so
the tile could only ever fail for officially configured users. Removed
across server, shared UI, and the VS Code extension; the provider logo
fallback stays — it serves the model picker, not usage.

CHANGELOG.md

@@ -23,6 +23,7 @@ All notable changes to this project will be documented in this file.
 - Chat: a "Follow new content while streaming" checkbox (Settings → Chat → Streaming, on by default) turns automatic following off entirely; with it off, the scroll-to-bottom pill now appears as soon as the reply grows past the visible area.
 - Command palette: rarely used commands (pin session, copy session ID, multi-run launcher, archived sessions, notes, todos, status, theme) are found by typing but stay off the first screen.
 - Mobile: narrowing a browser window past phone size switches into the mobile layout (and back when widened); the old/new mobile layout setting is gone.
+- Usage: the Command Code tile is gone — their official API exposes no usage data, so the tile could only fail.
 - Auth: an expired OpenChamber login is announced within seconds by a banner with a Log in button, instead of being discovered through failing actions. Sending pauses until login, and a conversation that failed to load reloads itself afterwards.
 - Chat: a failed send returns your typed prompt to the input — whatever the reason — instead of losing it to an error toast; a mid-send session switch lands it in that session's draft.
 - Chat: opening a session or resizing panels could strand the view in a large empty space below the last message; the list now returns to the real end, and a width resize keeps a reader who was at the bottom at the bottom.