Add session-budget, weekly-budget, and peak-hours widgets

[actionk]

Summary

Three new widgets for tracking Claude Code usage budget and Anthropic peak hours:

• session-budget — Shows 5-hour session usage with a surplus/deficit indicator relative to linear pacing. Example: 5h: 32% ↓34% means usage is 34% below the expected pace (you have headroom). ↑ means you're burning faster than expected.
• weekly-budget — Same concept applied to the 7-day rolling window. Example: Week: 27% ↓9%
• peak-hours — Shows whether Anthropic's peak hours are active (weekdays 5am–11am PT / 1pm–7pm GMT) with a countdown to the next toggle. Example: ⚡ Peak 3h20m or Off-peak 17h37m

How budget indicators work

Expected usage = (elapsed time / total window) × 100%
Difference = actual − expected

↓ = under budget (good — headroom remaining)
↑ = over budget (burning fast)

Widget types

Type	Category	Raw Value	Colors
session-budget	Usage	✅	✅
weekly-budget	Usage	✅	✅
peak-hours	Usage	❌	✅

Implementation details

• Reuses existing resolveUsageWindowWithFallback and resolveWeeklyUsageWindow utilities for elapsed/remaining time calculation
• Reuses formatRawOrLabeledValue, getUsageErrorMessage shared helpers
• Peak hours uses Intl.DateTimeFormat with America/Los_Angeles timezone for reliable cross-locale PT conversion
• All widgets follow the standard Widget interface pattern with preview mode support

Test plan

• SessionBudget — 8 tests (preview, null data, errors, under/over budget arrows, raw value, clamping)
• WeeklyBudget — 7 tests (preview, null data, errors, under/over budget, raw value)
• PeakHours — 5 tests (preview, peak detection, off-peak detection, weekends, non-null guarantee)
• All 20 tests pass
• Lint clean (zero warnings)
• No regressions in existing widget tests