Merge Luma launcher fork into monorepo

Move trampoline files (boot-hook, watcher, overlay) into trampoline/
subdirectory. Add upstream Luma v2.3.1 source at repo root with our
additions:

- Page::Ha (4th nav tab) with placeholder empty state
- HA tab config schema and default entity mapping (ha-home/)
- Nav keys renamed: "home" → "start", new "ha" tab between Apps and Settings
- All state.rs/view.rs/main.rs/tests.rs updated for 4-tab navigation

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

flake.nix

@@ -0,0 +1,86 @@
+{
+  description = "Luma Rust/SDL2 development and packaging environment";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs =
+    { nixpkgs, rust-overlay, ... }:
+    let
+      systems = [
+        "aarch64-darwin"
+        "aarch64-linux"
+        "x86_64-linux"
+      ];
+      forEachSystem =
+        f:
+        nixpkgs.lib.genAttrs systems (
+          system:
+          f (
+            import nixpkgs {
+              inherit system;
+              overlays = [ rust-overlay.overlays.default ];
+            }
+          )
+        );
+      project = builtins.fromJSON (builtins.readFile ./package.json);
+      pnpmVersion = nixpkgs.lib.removePrefix "pnpm@" project.packageManager;
+    in
+    {
+      devShells = forEachSystem (
+        pkgs:
+        let
+          # Match the native CI toolchain and include the TV's soft-float Rust std.
+          rust = pkgs.rust-bin.stable."1.93.0".minimal.override {
+            extensions = [
+              "clippy"
+              "rustfmt"
+            ];
+            targets = [ "armv7-unknown-linux-gnueabi" ];
+          };
+          pnpm =
+            assert pkgs.lib.assertMsg (
+              pkgs.pnpm_10.version == pnpmVersion
+            ) "The flake's pnpm must match package.json; update flake.lock and packageManager together.";
+            pkgs.pnpm_10;
+        in
+        {
+          default = pkgs.mkShell ({
+            name = "luma";
+            packages = [
+              pkgs.nodejs_24
+              pnpm
+              rust
+              pkgs.pkg-config
+              pkgs.SDL2
+              pkgs.woff2
+              (pkgs.python3.withPackages (python: [ python.fonttools ]))
+              pkgs.cmake
+              pkgs.git
+            ]
+            ++ pkgs.lib.optionals pkgs.stdenv.hostPlatform.isLinux [
+              pkgs.libGL
+              pkgs.mesa
+              pkgs.xvfb-run
+            ];
+          });
+        }
+      );
+
+      formatter = forEachSystem (
+        pkgs:
+        pkgs.writeShellApplication {
+          name = "luma-nixfmt";
+          runtimeInputs = [ pkgs.nixfmt ];
+          text = ''
+            exec nixfmt "$@" flake.nix
+          '';
+        }
+      );
+    };
+}