Zmk v0.3.0 - #3

Last touched 2022-03 against zmk main (Zephyr 2.5, LVGL 7.6.1); this
brings both board definitions to the v0.3.0 release. Both halves build
clean in zmk-build-arm:stable (left 33.7% flash / 24.8% RAM, right
28.6% / 18.2%). Full excavation and rationale: zmk-portability-report.md.

Build system:
- Pin west.yml to v0.3.0; add build.yaml + CI via shared workflow
- Native CONFIG_BUILD_OUTPUT_UF2 replaces the uf2conv.py post-build hook

Devicetree:
- SPI pins to pinctrl (sck/mosi-pin removed in Zephyr 3.0); MISO freed
- zephyr,display chosen node (panel no longer found by device name)
- wakeup-source on kscan; deprecated label properties dropped

Kconfig:
- LVGL_* -> LV_*/LV_Z_* namespace; UNSCII-8 pinned as default + theme
  small font (resolution now comes from DT width/height)
- board.c deleted: VDDH DC/DC now via BOARD_ENABLE_DCDC_HV=y; broken
  BOARD_ENABLE_DCDC dependency fixed but kept off (deliberate, see report)
- BT_MAX_CONN/BT_PERIPHERAL_PREF_* dropped: role-aware defaults give
  6/12/30/400 - same interval as the old hand-tune plus slave latency 30
- ZMK_USB central-only per upstream; right keeps bare USB stack so the
  CHG indicator still works
- Display stack 2048->4096, LV_Z_MEM_POOL_SIZE=8192 (crash hypothesis)
- RC oscillator and 2/10 debounce preserved with rationale comments

Widgets (LVGL 7 -> 8):
- battery: zmk_battery_state_of_charge() replaces bt_bas polling
- output: endpoint-instance API on central (profile nicknames kept);
  new peripheral branch on zmk_split_bt_peripheral_is_connected() -
  v0.3.0 no longer compiles endpoint/profile APIs on peripherals
- layer: zmk_keymap_layer_name() + index-to-id hop; keymap layers
  renamed label -> display-name
- WPM widget retired (unused)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Three issues from the first on-hardware test of the v0.3.0 migration,
all display-only (matrix/BLE/combos/layers verified working):

- ZMK_DISPLAY_INVERT=y on both halves: LVGL 8's mono theme defaults to
  the light variant, LVGL 7 defaulted dark - restores white-on-black.

- Layer label row 41 -> 39: lv_font_unscii_8 declares line_height 9 in
  LVGL 8 (was 8 in LVGL 7), so 41+9 overran the 48-row panel.

- SSD1306 width 96 -> 128 (full controller RAM): the glass shows a
  64-column window whose edge includes ~4 RAM columns a 96-wide
  framebuffer never writes. Their power-on garbage was invisible for
  four years under the dark theme (unwritten = off = black-on-black)
  and surfaced as a lit 4px bar after the theme migration. Rendering
  all 128 columns keeps every reachable column painted; content
  position on glass is unchanged (widgets stay anchored at x=32).

Both halves rebuilt and verified on hardware.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>