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_wasuro.md

@@ -1 +1,38 @@
-# Placeholder
+# compile_wasuro.sh
+
+Pulls the Wasuro WASM runtime Pascal sources into the build tree.
+
+## Overview
+
+`compile_wasuro.sh` fetches the Wasuro WebAssembly runtime from its Git repository using a sparse checkout (only the `src/wasm` subtree) and copies the Pascal source files into the local `wasuro/` directory. This makes the Wasuro units available to the FPC compiler via `-Fu` include paths during `compile_sources.sh`.
+
+## Prerequisites
+
+- `git` must be available and able to reach `https://gitea.spexeah.com/Spexeah/Wasuro.git`.
+- The `find` and `cp` utilities must be available.
+
+## Inputs
+
+| Source | Description |
+|--------|-------------|
+| Wasuro Git repository | Cloned (sparse, depth 1) from the `develop` branch. |
+
+## Outputs
+
+| File | Description |
+|------|-------------|
+| `wasuro/*.pas` | Pascal source files for the WASM runtime, ready for inclusion in the FPC build. |
+
+## Behavior
+
+1. **Cache check**: If `.pas` files already exist in `wasuro/`, the script prints a message and exits immediately, skipping the network fetch.
+2. **Sparse clone**: Clones the Wasuro repository into `/tmp/wasuro` with `--depth 1`, `--filter=blob:none`, and `--sparse`, then sets the sparse-checkout to `src/wasm`.
+3. **Copy**: Copies the contents of the cloned `src/wasm/` directory into `wasuro/`.
+4. **Cleanup**: Removes the temporary clone from `/tmp`.
+5. Reports the number of Pascal files copied.
+
+## Notes
+
+- The sparse checkout minimizes download size by fetching only the `src/wasm` subtree.
+- Once `wasuro/` is populated, subsequent builds reuse the cached files without re-cloning. To force a fresh pull, delete the `wasuro/` directory.
+- The script uses `set -e`, so any failure (network error, git error) aborts the build.