feat(lang): 0.S - a reference out of a read-only state is read-only (named so), a program's type named like the runtime's is refused (PadButton), tests for both, the migrate case covers lets; changeset

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

changes/state.md

@@ -0,0 +1,27 @@
+bump: major
+type: feature
+**No function writes a global: a module's changing data is a `state`.** `state Hiker { hips: int =
+-1 }` is a record with exactly one instance, which no code can name; it reaches code as a parameter,
+`h: mut Hiker` to change it or `h: Hiker` to read it, and the runtime supplies it at the entry points
+(`entry (h: mut Hiker)`, a handler's, a listener's or a lifecycle hook's parameters, a scene's `on
+enter (h: mut Hiker)`, a test's, a `ui` block's `Hiker.hips`, a function value - a system's, a port
+bind's, a package's callback - an engine system, a namespace method's target and every call into the
+runtime). A module-level `var` is refused; a module-level `let` is immutable all the way down. A
+read-only state is checked where it is written - an assignment or a `push` through it or through a
+local holding part of it, passing it where `mut` is wanted, a `machine` over its field - and so is a
+module-level `let`. Each test block gets fresh states. A program's type named like one the runtime
+declares (`property PadButton` beside the runtime's `enum PadButton`) is refused instead of failing
+in clang.
+
+`ludic migrate state [file|dir...] [--runtime] [--dry-run]` moves programs there: a var nothing
+writes becomes a `let`, each module's other vars one state (`FishingState`, `Render3dState`,
+`SceneDemoState`), every reference `fishing_st.name`, each function's states - to a fixed point over
+what it calls - its leading parameters, `mut` where anything below it writes, and each entry point
+declares them; the plans of every program given are merged before a file is edited. gpp's 35
+mechanic packages, ludic.ui, ludic.render3d, every example, the docs' fences and the runtime were
+moved with it. The toolchain's own programs build with `--globals` until they move too.
+
+Outside the runtime, the drawable's size and scale, the screen's framebuffer and the tilemap's tile
+size are read and set through its functions (`gl_width()`, `gl_set_drawable(w, h)`,
+`gl_screen_fbo()`, `gl_pixel_scale()`, `rt_map_tile_size()`), and ludic.ui's render3d backend
+installs itself through the `UiRenderers` registry.