Add AMOLED-1.8 board + device-abstraction refactor for community ports

[tobby168]

Summary

Two related changes that together make the project welcoming to new
board ports:

1. Add Waveshare ESP32-S3-Touch-AMOLED-1.8 support (the existing
   commit you'd already see in my fork — SH8601 + FT3168 + XCA9554,
   368×448 portrait).
2. Device-abstraction refactor that follows it: a thin HAL in
   firmware/src/hal/ + per-board folders under firmware/src/boards/
   instead of the build-flag-driven #ifdef BOARD_* sprawl the second
   port introduced. Shared code (main.cpp, ui.cpp, splash.cpp) is
   now #ifdef-free.

After this lands, adding a third board (or letting somebody else add
theirs) is cp -r firmware/src/boards/template firmware/src/boards/<new>/,
edit the TODOs, add a PlatformIO env. No shared file touches.

What changed

HAL (firmware/src/hal/) — public interfaces shared code calls:
display_hal, touch_hal, input_hal, power_hal, imu_hal,
board_caps. Compile-time selection via PlatformIO's build_src_filter,
not virtual functions — no vtable cost.

Per-board folders (firmware/src/boards/):

• waveshare_amoled_216/ — CO5300 + CST9220 + AXP PKEY + QMI8658 rotation
• waveshare_amoled_18/ — SH8601 + FT3168 + AXP + XCA9554 (PWR via EXIO4), no rotation
• template/ — copy-this-to-start-a-port skeleton

Each board owns its board.h (pins, I2C addrs, BOARD_HAS_* flags),
board_init.cpp (Wire.begin + any IO expander release), display.cpp,
touch.cpp, input.cpp, power.cpp, imu.cpp, caps.cpp, plus any
board-private hardware drivers.

Responsive UI: ui.cpp::compute_layout() picks fonts and layout
from board_caps() at runtime — current breakpoints H ≥ 460 → large,
else compact. splash.cpp computes CELL = min(W, H) / 20 instead of
the two hardcoded values from the previous port.

Capability flags: BoardCaps (runtime struct) for things shared
code queries; BOARD_HAS_* (compile-time macros) for things the linker
can dead-strip per board. See docs/porting/capability-flags.md.

Docs: docs/porting/{adding-a-board, hal-contract, capability-flags}.md.

Deleted from src/ root (moved into boards// or hal/):
display_cfg.h, power.{h,cpp}, imu.{h,cpp}, io_expander.{h,cpp}.

Stats

• 30+ #ifdef BOARD_* blocks across 6 files → 0 in shared code
• main.cpp shrinks from ~590 lines to ~250
• ui.cpp Layout struct replaces ~3 separate #ifdef BOARD_AMOLED_18 blocks for fonts/dimensions

Test plan

• pio run -d firmware -e waveshare_amoled_216 succeeds
• pio run -d firmware -e waveshare_amoled_18 succeeds
• AMOLED-1.8 flashed + screenshots verified for splash / usage / bluetooth — pixel-identical to pre-refactor (see screenshots/amoled_18/)
• AMOLED-2.16 board hardware smoke test (only AMOLED-1.8 was attached during this verification pass)
• HID buttons (Space / Shift+Tab / PWR) on both boards

Notes for review

• Other open PRs (Activity screen: live Claude Code session state from hooks #22 Activity screen, Auto-sleep screen after 30 min idle #24 auto-sleep) live on separate
  branches in my fork. They're sequenced — once Activity merges, I'll
  rebase those on top of this refactor; the refactor pattern absorbs
  the Activity-screen #ifdefs cleanly (already done in my downstream).
• Touch driver policy is documented in docs/porting/hal-contract.md:
  contributors choose any library that fits the contract; the FT3168
  vendored reader pattern is what we used to avoid GPL'ing the project.
• The HAL is intentionally compile-time-only — build_src_filter
  ensures only one board's display.cpp/touch.cpp/etc. links into
  each env. Runtime BoardCaps is for things UI / main loop need to
  query (button count, has_battery, etc.) so shared code doesn't need
  to branch on board identity at all.

🤖 Generated with Claude Code

[HermannBjorgvin]

Built and works perfectly on my board. This is a really nice contribution thank you, especially the template and the instructions on adapting other boards, much appreciated!

[tobby168]

@HermannBjorgvin I am not able to merge it, can you help? thanks

[HermannBjorgvin]

Yes merged and rebased the activity-stream branch