feat(status): battery health scoring and uptime warning

[sebastianbreguel]

Summary

Adds two health indicators to mo status that surface actionable information already collected but not highlighted:

• Battery health scoring: The Power card now shows a color-coded health label (Healthy / Fair / Service Soon) based on cycle count (500/900 thresholds) and capacity (90%/80% thresholds). Cycle count text is also color-coded.
• Uptime warning: Uptime in the header is now color-coded — green for ≤7 days, yellow for 7–14 days, red with ↻ indicator for >14 days suggesting a restart.
• Both metrics contribute small penalties to the overall health score.

These were discussed in #659 as features that fit naturally inside mo status without creating overlap.

What changed

File	Change
metrics.go	Added UptimeSeconds field to MetricsSnapshot
metrics_health.go	Added battery/uptime thresholds, penalties in health score, batteryHealthLabel() and uptimeSeverity() helpers
metrics_health_test.go	3 new test functions covering label logic, severity, and score penalties
view.go	Color-coded uptime in header, health label + colored cycles in Power card

Test plan

• go build ./cmd/status/ — compiles cleanly
• go vet ./cmd/status/ — no issues
• go test ./cmd/status/ — all 55 tests pass
• JSON output includes uptime_seconds and battery data
• Visual verification: battery label renders correctly, uptime colors work

[sebastianbreguel]

Visual Preview

Power Card — Before vs After

Before (raw data only):

◪ Power  ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
Level  ████████████░░░░  70.0%
Health ████████████████  100%
Discharging · 3h 20m · 8W
Normal · 19 cycles · 42.5°C

After (health label + colored cycles):

◪ Power  ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
Level  ████████████░░░░  70.0%
Health ████████████████  100%
Discharging · 3h 20m · 8W
🟢 Healthy · 19 cycles · 42.5°C

With aging battery (600 cycles, 87% capacity):

◪ Power  ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
Level  ████████████░░░░  72.0%
Health ██████████████░░   87%
Discharging · 2h 45m · 9W
🟡 Fair · 600 cycles · 45.2°C

With worn battery (950 cycles, 74% capacity):

◪ Power  ╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌╌
Level  ██████████░░░░░░  65.0%
Health ████████████░░░░   74%
Discharging · 1h 50m · 11W
🔴 Service Soon · 950 cycles · 48.1°C

Header — Uptime Warning

Normal (≤7 days):

Status  Health ● 94  MacBook Pro · Apple M4 Pro · 24GB/460GB · macOS 26.3 · up 1d 4h

Warning (7–14 days, yellow):

Status  Health ● 92  MacBook Pro · Apple M4 Pro · 24GB/460GB · macOS 26.3 · ⚠ up 10d 5h

Danger (>14 days, red + restart indicator):

Status  Health ● 89  MacBook Pro · Apple M4 Pro · 24GB/460GB · macOS 26.3 · 🔴 up 18d 2h ↻

Health Score Impact

Condition	Penalty	Example
Cycles 500–900	-2	Score 98 → 96
Cycles >900	-5	Score 98 → 93
Capacity 80–90%	-2	Score 98 → 96
Capacity <80%	-5	Score 98 → 93
Uptime 7–14 days	-1	Score 98 → 97
Uptime >14 days	-3	Score 98 → 95