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/loc.md

@@ -1 +1,30 @@
-# Placeholder
+# loc.sh
+
+Counts the total lines of Pascal source code in the project.
+
+## Overview
+
+`loc.sh` is a utility script that counts the total number of lines across all `.pas` files in the project. It is called by `compile_vergen.sh` to embed a line count into the kernel's version metadata.
+
+## Prerequisites
+
+- `find`, `xargs`, `wc`, and `awk` must be available.
+
+## Inputs
+
+All `*.pas` files found recursively from the current working directory.
+
+## Outputs
+
+Prints a single line to stdout containing the total line count (e.g., `42567`).
+
+## Behavior
+
+1. Uses `find` to locate all `.pas` files starting from the current directory.
+2. Pipes the file list to `xargs wc -l` to count lines in each file.
+3. Uses `awk` to extract the grand total from the last line of `wc` output.
+
+## Notes
+
+- The output is consumed by `compile_vergen.sh` via command substitution and piped through `awk` to extract just the numeric value.
+- This script produces no files; it only writes to stdout.