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_sources.md

@@ -1 +1,55 @@
-# Placeholder
+# compile_sources.sh
+
+Compiles the Asuro kernel Pascal sources with Free Pascal.
+
+## Overview
+
+`compile_sources.sh` invokes the Free Pascal Compiler (FPC) to compile the main kernel unit (`src/asuro.pas`) along with all dependent units. It dynamically discovers every subdirectory under `src/`, `wasuro/`, and `compat/` and passes them as unit search paths (`-Fu`) so that FPC can resolve all unit references.
+
+## Prerequisites
+
+- `fpc` (Free Pascal Compiler 3.2.2 or compatible) must be available.
+- `find` must be available.
+- The `src/`, `wasuro/`, and `compat/` directories must be populated with their respective Pascal sources.
+- The `lib/` output directory must exist.
+
+## Inputs
+
+| Source | Description |
+|--------|-------------|
+| `src/asuro.pas` | The top-level kernel program unit. |
+| `src/**/*.pas` | All kernel Pascal source units. |
+| `wasuro/**/*.pas` | Wasuro WASM runtime units (pulled by `compile_wasuro.sh`). |
+| `compat/**/*.pas` | Compatibility layer units. |
+
+## Outputs
+
+| File | Description |
+|------|-------------|
+| `lib/*.o` | ELF object files for each compiled unit. |
+| `lib/*.ppu` | FPC precompiled unit files. |
+
+## Behavior
+
+1. Discovers all subdirectories under `src/`, `wasuro/`, and `compat/` using `find`.
+2. Builds a `-Fu` flag string containing every discovered directory.
+3. Invokes `fpc` with the following key flags:
+   - `-Aelf` -- Output ELF-format assembly.
+   - `-gw -g -gl` -- Generate DWARF debug info and line info.
+   - `-n` -- Ignore `fpc.cfg`; do not load default configuration.
+   - `-v0e` -- Verbosity: errors only.
+   - `-O3` -- Aggressive optimization.
+   - `-OpPENTIUM3` -- Optimize for Pentium III instruction scheduling.
+   - `-Si -Sc -Sg` -- Enable inline, C-style operators, and goto support.
+   - `-Xd` -- Do not search default library path.
+   - `-CX -XXs` -- Create smartlinkable units and strip unused code.
+   - `-CfSSE -CfSSE2` -- Use SSE/SSE2 floating-point.
+   - `-Rintel` -- Use Intel assembler syntax.
+   - `-Pi386 -Tlinux` -- Target i386 Linux (ELF).
+   - `-FElib/` -- Output compiled files to `lib/`.
+
+## Notes
+
+- The `-n` flag is critical: it prevents FPC from loading any system-wide configuration that might introduce incompatible settings for the bare-metal target.
+- The `-Xd` flag ensures FPC does not try to link against system libraries, since the kernel is freestanding.
+- Object files produced here are later consumed by `compile_link.sh`.