oxiforge 0.3.0

A memory-efficiency release on oxivgl 0.4.0: generated views now pay one
lv_style_t per distinct style treatment instead of per widget, the last
per-create heap leaks are gone, new YAML surface covers background images
and per-view resource budgets, and the JSON schema is generated from the
model types.

Added

• Background-image style props — bg_image_src (an extern
  lv_image_dsc_t symbol; oxiforge emits the declaration, the app links the
  asset), bg_image_opa, bg_image_recolor, bg_image_recolor_opa,
  bg_image_tiled. Usable in style_definitions, inline widget styles,
  state/part styles, and directly on pages — a whole-screen backdrop is a
  page-level styles: ref. (#30)
• Per-view resource budgets. budget: { max_objects, max_depth } on a
  page or toast emits oxivgl::diag::assert_budget after creation — a
  debug-build tripwire so a widget-count regression fails CI/HIL instead of
  OOMing a constrained target. No-op in release builds. (#33)
• The JSON schema is now generated from the model types (schemars behind
  the new schema feature; gen_schema bin) and covers all 34 widgets and
  every property the parser accepts — the previous hand-written schema was
  stale at the 0.1.0 surface and structurally rejected valid documents. A CI
  drift test fails when model.rs changes without regeneration. (#35)

Changed

• oxivgl dependency bumped 0.3.3 → 0.4.0 — shared-style model
  (deprecated inline setters), diag resource toolkit, background-image
  API. (#30)
• Referenced styles are built once per create_*() and shared by every
  referencing widget (hoisted let style_<id> = style_<id>();). Previously
  N references built N duplicate lv_style_t, resident for the view's
  lifetime. Zero visual change. (#30)
• Page/toast-level style props build a shared Style applied via
  add_style instead of the Obj inline setters deprecated in oxivgl
  0.4.0. The old screen-only prop subset is gone: previously
  silently-dropped page props (pad_all, radius, …) are now emitted. (#30)
• Structurally identical anonymous styles are deduplicated within a
  create_*() — inline/state/part styles with the same setter body share
  one lv_style_t. (#32)
• model::Page, model::ToastDef gained a budget field and
  model::StyleProps gained the bg_image_* fields — code constructing
  these types literally must add the new fields; the YAML schema is purely
  additive. (#30, #33)

Fixed

• Grid-track and AnimImg frame arrays no longer leak per create_*().
  Both are compile-time constants and now live in function-local statics
  (frame arrays behind a generated Sync wrapper) instead of
  Box::leak — previously an accumulating leak on any repeatedly-opened
  view using layout: grid or anim_img. (#31)
• A one-sided grid_columns/grid_rows no longer generates
  uncompilable code — the absent axis gets a terminator-only dsc
  array. (#31)
• Image symbols in toasts are now declared. Symbol collection scans
  pages and toasts — AnimImg/Imagebutton sources inside a toast
  previously produced undeclared-symbol errors. (#30)
• style_definitions gradient refs are validated (previously
  unchecked); bg_image_src is validated as a Rust identifier. (#30)
• Documentation rot swept. README/CLAUDE.md no longer describe the
  abandoned Box::leak + mem::forget model; the YAML spec documents the
  full 0.2.0/0.3.0 surface (events, toasts, views, feature-gated widgets)
  and marks theme: as reserved; CR docs carry resolution statuses. (#36)