[NellowTCS]

Description

Moves the PocketMage library out of the OS tree into its own SDK (PocketMage_SDK) and replaces the OTA-app model with ELF apps. Apps are built against the SDK and loaded in-process from the SD card. Installing or running one doesn't need a reflash or a reboot.

SDK split

• lib/PocketMage is gone. The SDK now lives in TalismanDesign/PocketMage_SDK and is pulled in as a submodule at Code/PocketMageOS/lib/PocketMage_SDK.
• Shared state (vspi/hspi/global_fs/prefs, settings, AppState/KBState, getBatteryVoltage) is now owned by the SDK. include/config.h is removed and globals.h pulls everything from the SDK header.
• The OTA_APP / OTA_APP_FLAG switch is replaced by PM_TARGET_HOST (the OS) and PM_TARGET_APP (an app). The old OTA_APP: tags in the codebase are renamed to match.
• i18n generation moved into the SDK (pocketmage_i18n/tools/gen_i18n.py). Catalogs merge in order: SDK base first, then the OS's own src/i18n.

ELF apps (elf_runner.cpp, elf_app_manifest.cpp)

• An app is a .app.elf packed in a .tar with a <name>_ICON.bin and an optional .elfo overlay. The app loader installs it into one of 4 slots (/apps/slot1–/apps/slot4), tracked in NVS as ELFINFO1–ELFINFO4.
• runElfApp() relocates the image with esp_elf_relocate_source() through a file-backed elf_source_t, so the whole .app.elf is never held in RAM. The app's main runs in its own task, and the OS loop and E-Ink task stand down while CurrentAppState == ELFAPP.
• Exiting is just a return from main. The image is unloaded and the OS goes back to HOME without rebooting.
• If there's a matching .elfo, it's loaded through elf_overlay, and the entry point is redirected through its stub block.
• An optional app.properties file sets name, version, author and scope. scope limits which pm_* symbols the app can resolve. libc, libstdc++ and ESP-IDF stay reachable no matter the scope. A missing or unreadable manifest falls back to the ELF base name and doesn't block the app.
• The host exports a curated symbol set (src/ELF_SYMS/esp_all_symbol.cpp), including pocketmage_sdk_version.
• Legacy OTAINFO* / OTA* NVS keys are cleared when a slot is cleared, so old bin-era installs disappear on upgrade.

Submodules (.gitmodules)

• lib/PocketMage_SDK → TalismanDesign/PocketMage_SDK
• lib/elf_loader/esp-iot-solution → TalismanDesign/esp-iot-solution, pinned to pocketmage-pin-1.3.3 (this carries the elf_loader streaming source API)
• lib/elf_overlay → TalismanDesign/elf_overlay

CI

• Dropped the OTA_APP build env and its tar packaging step.
• New example-app job: installs the SDK and the Xtensa toolchain (pinned and checksummed), builds the elf_overlay host tools, then builds and packs the SDK template app and runs pm check on it. It also checks that the ELF is little-endian and that the tar has the .app.elf, .elfo and icon.
• i18n-check now regenerates from the stored catalogs and checks that the app catalog actually merged into the SDK tables.
• Firmware and web-flasher workflows read app0 from partitions.csv instead of partitions_4APP.csv.
• Checkouts use submodules: recursive.

Docs

• New Docs/docs/guides/elf-apps.md covering building, packaging, installing, and what an app can rely on.
• CONTRIBUTING.md no longer mentions pio run -e OTA_APP and points to the ELF apps guide.

Breaking changes

• OTA apps (app.bin in a tar) are no longer supported. Existing installs need to be rebuilt against the SDK as .app.elf.
• Fresh clones need git submodule update --init --recursive. Nothing builds without the SDK.
• Anything that included config.h or the old lib/PocketMage headers directly needs to go through the SDK now.

Testing

• Target: ESP32-S3, built through Arduino-ESP32 3.3.11 / ESP-IDF 5.5.5 (pioarduino 55.03.311)
• PM_PRODUCTION: TODO
• PM_BETA (no PSRAM): TODO
• Installed and ran an ELF app from the loader: TODO
• Scoped app.properties rejects out-of-scope pm_* symbols: TODO

All 9 CI checks pass (firmware builds for both envs, example-app, i18n-check, docs-build, CodeQL).