refactor(api)!: one namespace per feature, screen split out

Namespaces were shared across features: `settings` was written by core, the
panel and touch, and `input` by touch and buttons. That made "does this
firmware implement the whole feature?" a question no pointer could answer.

Each namespace now belongs to exactly one feature or to core, so a feature is
a provider pointer and the compiler validates completeness:

  gui, node       -> screen, tree, under the screen feature
  settings        -> screen (rotation, theme), sys (timezone),
                     touch (calibration)
  input           -> touch, buttons

Runtime::open() no longer requires a GuiProvider; a firmware without one runs
with no screen/tree globals and reports sys.hasFeature("screen") false.
Rotation is one value again: GuiProvider::setRotation applies and persists, so
an app rotating the panel transiently puts the old value back itself.

native/include/lua/providers.h

@@ -35,19 +35,6 @@ struct MemoryInfo {
   int32_t largestFreeBlock;
 };
 
-class SettingsProvider {
-public:
-  virtual ~SettingsProvider() = default;
-  virtual int32_t rotation() const = 0;
-  virtual Status setRotation(int32_t degrees) = 0;
-  virtual std::string timezone() const = 0;
-  virtual Status setTimezone(const std::string& timezone) = 0;
-  // Only the name of a palette; the colours themselves live in Lua, so the
-  // firmware can read the saved theme before a lua_State exists.
-  virtual std::string theme() const = 0;
-  virtual Status setTheme(const std::string& theme) = 0;
-};
-
 // Only what the firmware alone can answer. App identity, titles, data paths,
 // feature reporting and navigation are the runtime's, because it owns app
 // loading and knows which providers exist.
@@ -57,6 +44,8 @@ public:
   virtual int32_t millis() const = 0;
   virtual MemoryInfo memory() const = 0;
   virtual bool isClockSynced() const = 0;
+  virtual std::string timezone() const = 0;
+  virtual Status setTimezone(const std::string& timezone) = 0;
 };
 
 // Scripts are streamed rather than slurped: a whole module in one buffer needs
@@ -115,7 +104,13 @@ public:
   virtual int32_t width() const = 0;
   virtual int32_t height() const = 0;
   virtual int32_t rotation() const = 0;
-  virtual void setRotation(int32_t degrees) = 0;
+  // Applies the rotation and persists it, so the panel comes back the way the
+  // user left it with no second call to forget.
+  virtual Status setRotation(int32_t degrees) = 0;
+  // Only the name of a palette; the colours themselves live in Lua, so the
+  // firmware can read the saved theme before a lua_State exists.
+  virtual std::string theme() const = 0;
+  virtual Status setTheme(const std::string& theme) = 0;
   virtual int32_t color(int32_t r, int32_t g, int32_t b) const = 0;
   virtual void clear(int32_t color) = 0;
   virtual void fillRect(int32_t x, int32_t y, int32_t w, int32_t h,

native/include/lua/runtime.h

@@ -25,15 +25,14 @@ constexpr const char* MAIN_PATH = "/.lua/main.lua";
 // registered.
 struct Providers {
   LogProvider* log = nullptr;
-  SettingsProvider* settings = nullptr;
   SysProvider* sys = nullptr;
   FsProvider* fs = nullptr;
-  GuiProvider* gui = nullptr;
   HttpProvider* http = nullptr;
   TimerProvider* timer = nullptr;
   WifiProvider* wifi = nullptr;
   BleProvider* ble = nullptr;
 
+  GuiProvider* gui = nullptr;
   TouchProvider* touch = nullptr;
   ButtonsProvider* buttons = nullptr;
 };
@@ -82,7 +81,6 @@ public:
   bool applyPendingNavigation();
 
   LogProvider& log() const { return *providers_.log; }
-  SettingsProvider& settings() const { return *providers_.settings; }
   SysProvider& sys() const { return *providers_.sys; }
   FsProvider& fs() const { return *providers_.fs; }
   GuiProvider& gui() const { return *providers_.gui; }