Refine Usage screen typography and match Claude Code spinner easing

- Drop "Claude" prefix from titles, center all three
- Replace verbose "Current Session" / "Current Week" labels with rounded
  pills above the bar; reset countdown moves below the bar
- Extend bar to fill panel inner width (was 8px short)
- Symmetric vertical pill placement within panel
- Spinner: per-frame hold times + ping-pong indexing, modeled on
  Claude Code's Cavalry triangle oscillator (turn-around frames hold
  ~2x longer)
- Bottom spinner re-centered between weekly panel and screen edge
- screenshot.sh: 480x320 -> 480x480 for the new panel
- CLAUDE.md: document screenshot.sh + temporary boot-screen swap as
  the standard self-QA workflow for UI changes

CLAUDE.md

@@ -42,6 +42,12 @@ pio run -d firmware -t upload --upload-port /dev/ttyACM0  # flash (binary path u
 
 Device shows up as `/dev/ttyACM0` (Espressif USB JTAG/serial debug unit). No boot-mode gymnastics needed — direct flash works.
 
+## QA your own UI changes — don't ask the user
+
+The firmware ships a `screenshot` serial command that dumps the LVGL framebuffer over `/dev/ttyACM0`. `./screenshot.sh out.png /dev/ttyACM0` captures a 480×480 PNG. **Use this on every UI iteration** — Read the PNG with the Read tool, verify the change visually, iterate.
+
+The boot screen is `SCREEN_SPLASH` and only advances on a physical button press, so a fresh flash will sit on the splash. To screenshot the screen you're actually editing without asking the user to press a button, **temporarily change the default boot screen** in `main.cpp` (search for `ui_show_screen(SCREEN_SPLASH);`) to `SCREEN_USAGE` / `SCREEN_CONTROLLER` / `SCREEN_BLUETOOTH`, do your iteration, then revert before committing.
+
 ## Critical gotchas
 
 1. **CO5300 cannot rotate.** Its MADCTL only supports axis flips, not column/row exchange. Rotation is done by **CPU pixel remapping in `my_flush_cb`** in main.cpp. We use **PARTIAL render mode with strip rotation** (small 480×40 strips, fast). On rotation change → AMOLED brightness flash → force redraw.