Battery - Details widget: host renders

Evidence class: host render (Cairo/Pango via render::paint_home, no compositor, no board, no real sysfs). Date: 2026-10-15 (UTC). Change: openspec/changes/home-offers-a-battery-details-widget, task 2.1.

Command, from nix/rust-shell-client:

cargo run --example render_battery_details_evidence -- ../../docs/evidence/battery-details-widget/host

Source: examples/render_battery_details_evidence.rs, which builds each state by running the real home_widgets::battery::read_details over a temporary power_supply tree of fixture uevent files:

• charging-*: the BQ27220 gauge and BQ25896 charger uevent text read from the board on 2026-10-15 while charging over USB-C (55 percent, +600 mA, 4.202 V, 1627 / 3000 mAh, 38.1 C, 8160 s to full, charge type Fast).
• discharging-*: an invented fixture (71 percent, -412 mA, 3.89 V, 2025 / 2850 mAh, 37 cycles, 34.2 C, 2700 s to empty, charger offline). It is not a board capture.
• no-battery-*: only the charger supply present, so no Battery supply.
• picker-568x1232.png: the widget picker with the new row.

Sizes: 568x1232 (portrait panel), 1232x568 (landscape panel), 1280x800 and 1920x1080 (landscape HDMI). The wallpaper is a flat dark colour with four sample apps and a dock; the default theme (no Omarchy theme) is used.

Limits: these prove paint and layout of fixture values only. They do not show the board’s glass, real sysfs values on the running shell, the 10 s poll, or touch placement. The picker’s preview thumbnail is a small square crop, like the existing 4x2 clock rows. Board task 3.1 (operator places the widget and compares against /sys/class/power_supply) remains open. Current is rounded to 10 mA and power to 0.1 W in the display, so -412 mA shows as -410 mA.