docs: fill out compat, lvglh, and toolchain documentation

Replace placeholder content in doc/compat/, doc/lvglh/, and
doc/toolchain/ with comprehensive documentation derived from the
source files.

- compat: document Wasuro WASM VM compatibility shims
- lvglh: document LVGL v9.2.2 configuration, fonts, and patches
- toolchain: document all 13 build pipeline scripts

doc/toolchain/compile_sumgen.md

@@ -1 +1,35 @@
-# Placeholder
+# compile_sumgen.sh
+
+Generates an MD5 checksum badge for the final ISO image.
+
+## Overview
+
+`compile_sumgen.sh` computes the MD5 hash of `Asuro.iso` and downloads a shields.io SVG badge displaying the checksum. This badge is stored in the `release/` directory for use in project documentation and release pages.
+
+## Prerequisites
+
+- `md5sum`, `awk`, and `wget` must be available.
+- `Asuro.iso` must exist in the current directory (produced by `compile_isogen.sh`).
+- The `release/` directory must exist.
+
+## Inputs
+
+| Source | Description |
+|--------|-------------|
+| `Asuro.iso` | The final bootable ISO image. |
+
+## Outputs
+
+| File | Description |
+|------|-------------|
+| `release/checksum.svg` | Shields.io badge displaying the ISO's MD5 checksum. |
+
+## Behavior
+
+1. Computes the MD5 checksum of `Asuro.iso` using `md5sum`.
+2. Downloads a shields.io badge SVG with the checksum value and saves it to `release/checksum.svg`.
+
+## Notes
+
+- This script is not currently listed in the `compile.sh` pipeline. It may be invoked separately or have been superseded by badge generation in `compile_vergen.sh`.
+- The `wget` call is silenced (`-q`) and its stderr is redirected to `/dev/null`, so download failures are silent.