Add persistent script storage + hot-reload, verified live

lua_runtime now loads the running script from a new LittleFS-backed
drivers::storage (joltwallet/littlefs, the project's fifth external
managed component -- mounts the "storage" partition already reserved
in partitions.csv), falling back to the compiled-in default script
only on first boot. transport exposes GET/POST /api/script -- raw Lua
text, not JSON, since json_helpers.h can't round-trip scripts safely
-- relayed to lua_runtime via the same callback-registration pattern
already used for LedColorHandler, keeping transport free of a
dependency on lua_runtime. lua_runtime_reload() persists and hot-swaps
to a fresh Lua state immediately, no reboot.

Verified on real ESP32-C6 hardware: script loads via kvida-sdk, an
edited script hot-reloads within one tick, and the edit survives a
power cycle (proving LittleFS persistence, not just an in-RAM change).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

components/lua_runtime/include/lua_runtime.h

@@ -1,11 +1,14 @@
 #pragma once
 
+#include <cstddef>
+
 namespace kvida {
 
-// Creates the sandboxed Lua state and loads the default script (see
-// src/default_script.h). The script only *defines* the on_tick()
-// function -- call lua_runtime_tick() to actually run it. Call once at
-// boot.
+// Mounts storage and loads the script from there (see
+// components/drivers/include/storage.h), falling back to the compiled-in
+// default (src/default_script.h) if none is stored yet. The script only
+// *defines* the on_tick() function -- call lua_runtime_tick() to actually
+// run it. Call once at boot.
 void lua_runtime_init();
 
 // Calls the script's on_tick() global function -- one "wake, execute
@@ -14,4 +17,14 @@ void lua_runtime_init();
 // down the device.
 void lua_runtime_tick();
 
+// Persists `script` to storage and hot-reloads it into a fresh Lua
+// state, replacing whatever's currently running -- no reboot needed.
+// Wired to transport::set_script_change_handler() by main.cpp.
+void lua_runtime_reload(const char *script, size_t len);
+
+// Copies the currently-running script into buf (capacity cap), returns
+// the number of bytes written. Wired to transport::set_script_provider()
+// by main.cpp.
+size_t lua_runtime_current_script(char *buf, size_t cap);
+
 } // namespace kvida