Fixes for the new claude.ai layout.

The usage bars sit under the message box again. They had moved on top of the
buttons on a new chat, and dropped to the bottom of the page once you were in
a conversation.

The token count updates again when you switch between edited versions of a
message.

Fixed
- Usage bars now appear as soon as the page loads, instead of waiting for the token count to finish.
- Fixed an error response from claude.ai being read as usage data, which could cause repeated requests.
- Fixed image data inside tool results being counted as text, which made the token count far too high.
- Fixed some messages counting as zero tokens.

New: Claude Fable weekly usage

• The weekly usage bar now shows your Fable cap as a second fill in the bottom half of the bar (all-models weekly on top, Fable underneath) — no extra width, same tidy layout.
• The Fable half is color-coded to match claude.ai: teal when normal, gold at the warning level, red as you near the cap.
• Hover the weekly bar to see the exact split — "All models: X% · Fable: Y%" — plus the reset time.
• Fable usage is read directly from Claude's usage data, so it's the real number, not an estimate.
• Plans without a Fable limit look exactly as before.

Usage bars now show the exact reset time on hover — clock time for the 5-hour
session, weekday and date for the weekly window — instead of a generic description.