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_finish.md

@@ -1 +1,40 @@
-# Placeholder
+# compile_finish.sh
+
+Reports build status and generates the build result badge.
+
+## Overview
+
+`compile_finish.sh` is the final step in the Asuro build pipeline. It is sourced (not executed) by `compile.sh` and receives a single argument indicating whether the build succeeded or failed. It downloads the appropriate shields.io badge and exits with the corresponding exit code.
+
+## Prerequisites
+
+- `wget` must be available (though badge download failure is non-fatal).
+- The `release/` directory must exist.
+
+## Inputs
+
+| Input | Description |
+|-------|-------------|
+| `$1` | A string argument: `"failed"` or `"success"`. Passed by `compile.sh`. |
+
+## Outputs
+
+| File | Description |
+|------|-------------|
+| `release/build.svg` | A shields.io badge: red "build-failed" or green "build-succeeded". |
+
+## Behavior
+
+1. If `$1` is `"failed"`:
+   - Prints an error message directing the user to review the log.
+   - Downloads a red "build-failed" badge to `release/build.svg`.
+   - Exits with code 1.
+2. Otherwise:
+   - Prints a success message.
+   - Downloads a green "build-succeeded" badge to `release/build.svg`.
+   - Exits with code 0.
+
+## Notes
+
+- This script is sourced (`. compile_finish.sh`) by `compile.sh`, meaning its `exit` call terminates the parent shell. This is intentional -- it sets the final exit code for the entire build pipeline.
+- Badge download is silent and non-blocking; if `wget` fails (e.g., no network), the build still reports the correct exit code.