v0.5.0: projected weekly utilization (run-rate extrapolation)

Extrapolate where weekly usage lands at reset from how far through the
7-day window we are: current_pct / elapsed_fraction. 83% => on pace to
finish under the limit; 123% => on pace to exceed it, pace down.

Surfaced in three places matching the existing two-window layout:
- third tooltip line on hover
- third right-click menu line
- third progress bar in the floating panel (which now resizes to fit;
  Rotating cycles Session -> Weekly -> Projected)

First hour of a fresh window is floored so an early burst can't
extrapolate to an absurd flapping figure; exact linear run-rate after.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NDR7zhBJRiUYhbsULvNK7n