feat(runtime): embed platform modules as bytecode

ui.lua and hints.lua are compiled to LUA_32BITS bytecode (matching the
firmware's Lua build) and linked into the binary. A new package.searchers
entry checks them as the fallback after the SD card, so a local
/.lua/lib/ui.lua still shadows the packaged one for debugging.

Bytecode is ~40% smaller than source and loads without parsing. A fresh
SD card with no make sdcard now has the platform available.

tools/dump.c

@@ -0,0 +1,36 @@
+// Dumps a Lua source file as bytecode, linked against the same vendored Lua the firmware
+// runs (LUA_32BITS), so the header matches. Stand-in for luac when only the library is
+// vendored.
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "lauxlib.h"
+#include "lua.h"
+
+static int writer(lua_State*, const void* p, size_t size, void* ud) {
+  return fwrite(p, 1, size, (FILE*)ud) != size ? 1 : 0;
+}
+
+int main(int argc, char** argv) {
+  if (argc != 3) {
+    fprintf(stderr, "usage: %s input.lua output.luac\n", argv[0]);
+    return 1;
+  }
+  lua_State* L = luaL_newstate();
+  if (luaL_loadfilex(L, argv[1], "t") != LUA_OK) {
+    fprintf(stderr, "%s: %s\n", argv[1], lua_tostring(L, -1));
+    lua_close(L);
+    return 1;
+  }
+  FILE* out = fopen(argv[2], "wb");
+  if (!out) {
+    fprintf(stderr, "cannot open %s\n", argv[2]);
+    lua_close(L);
+    return 1;
+  }
+  const int err = lua_dump(L, writer, out, 1);  // strip debug info
+  fclose(out);
+  lua_close(L);
+  return err ? 1 : 0;
+}

tools/embed.py

@@ -0,0 +1,67 @@
+#!/usr/bin/env python3
+"""Compiles lua/lib/*.lua to LUA_32BITS bytecode and generates a C++ source file embedding
+the arrays. The runtime's module searcher checks these as a fallback after the SD card, so
+a local copy always shadows the packaged one.
+
+Usage:
+    tools/embed.py <luac32> <lua_lib_dir> <output.cpp> [--check]
+"""
+
+import subprocess
+import sys
+import pathlib
+
+HEADER = """\
+// GENERATED by tools/embed.py — do not edit. Run `make embed` to regenerate.
+#include <lua/embedded_modules.h>
+
+namespace esp32lua {
+
+"""
+
+FOOTER = """
+
+}  // namespace esp32lua
+"""
+
+
+def main():
+    check = "--check" in sys.argv
+    args = [a for a in sys.argv[1:] if a != "--check"]
+    if len(args) != 3:
+        sys.exit("usage: embed.py <luac32> <lua_lib_dir> <output.cpp> [--check]")
+
+    luac32, lib_dir, out_path = args
+    lib_dir = pathlib.Path(lib_dir)
+    out_path = pathlib.Path(out_path)
+
+    sources = sorted(lib_dir.glob("*.lua"))
+    arrays = []
+    rows = []
+    for src in sources:
+        import tempfile
+        with tempfile.NamedTemporaryFile(suffix=".luac", delete=False) as tmp:
+            tmp_path = tmp.name
+        subprocess.run([luac32, str(src), tmp_path], check=True)
+        bytecode = pathlib.Path(tmp_path).read_bytes()
+        pathlib.Path(tmp_path).unlink()
+        name = src.stem
+        comma = ", ".join(f"0x{b:02x}" for b in bytecode)
+        arrays.append(f"static const unsigned char {name}[] = {{{comma}}};\n")
+        rows.append(f'    {{"{name}", {name}, sizeof({name})}},')
+
+    footer = "const EmbeddedModule embedded_modules[] = {{\n{rows}\n}};\nconst size_t embedded_modules_count = {count};\n"
+    generated = HEADER + "".join(arrays) + footer.format(rows="\n".join(rows), count=len(sources)) + FOOTER
+
+    if check:
+        existing = out_path.read_text() if out_path.exists() else ""
+        if existing != generated:
+            sys.exit(f"{out_path} is stale; run `make embed`")
+        return
+
+    out_path.write_text(generated)
+    print(f"wrote {len(sources)} modules to {out_path}")
+
+
+if __name__ == "__main__":
+    main()