Integrate LSF allocator and lazy widget extension

[jserv]

This introduces a twin_raw_* indirection layer between the memory stats tracking (memstats.c) and the underlying allocator. When CONFIG_MEM_TLSF is enabled, allocations route through a self-contained TLSF (Two-Level Segregated Fit) allocator backed by a static pool, providing O(1) bounded-time malloc/free for real-time embedded targets. When disabled, twin_raw_* inlines to libc malloc/free with zero overhead.

The TLSF implementation is stripped to static-pool essentials (pool_init, malloc, realloc, free) and uses the portable twin_clz/twin_clzll helpers instead of raw compiler intrinsics. A key deviation from upstream TLSF: block_find_free() trims to the actual request size rather than the bin minimum, avoiding catastrophic internal fragmentation when small requests hit large bins.

Move optional widget fields (callback, callback_data, want_focus) into a lazily-allocated twin_widget_ext_t block. Widgets that never register a callback keep ext == NULL and save 16 bytes per widget (64-bit) or 8 bytes (32-bit). The copy_geom field stays inline in the base struct for app-level direct access. All call sites in box.c, button.c, and widget.c updated to use inline accessors.

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Summary by cubic

Add an optional TLSF-backed allocator and a lazy widget extension to reduce RAM use and improve real-time behavior. Adds a twin_raw_* allocator layer and moves optional widget fields out of the base struct.

• New Features

  • Optional TLSF allocator behind CONFIG_MEM_TLSF with a fixed pool (CONFIG_MEM_TLSF_POOL_SIZE). O(1) malloc/free; falls back to libc when disabled.
  • TLSF tweak: trims splits to the actual request size to reduce fragmentation.
  • New twin_raw_* allocator indirection; memory stats now track allocations via this layer. The tracking table itself stays on libc to avoid recursion.
  • Widgets: move callback, callback_data, and want_focus into a lazily allocated extension, saving 8–16 bytes per widget. Added twin_widget_set_focusable; twin_widget_set_callback unchanged. Call sites updated.

• Migration

  • Stop touching widget->callback, widget->callback_data, or widget->want_focus directly. Use twin_widget_set_callback(...) and twin_widget_set_focusable(...).
  • If enabling CONFIG_MEM_TLSF, size CONFIG_MEM_TLSF_POOL_SIZE for your workload (pixmaps can be large). Requests beyond the pool return NULL. No changes needed when TLSF is disabled.

^{Written for commit f224621. Summary will update on new commits.}

[cubic-dev-ai]

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