toolchain: gsinit зануляет _DATA (C-семантика статиков) + sprinter-cc --max-allocs

Все четыре crt0 (default/small/minimal/banked): gsinit теперь зануляет
_DATA и _BSS через общий zero_area, затем копирует _INITIALIZER.
Явные `= 0` у глобалов/статиков больше не нужны (они жгли байты
_INITIALIZER в образе). crt0-приватные переменные, записываемые ДО
gsinit (_estex_startup_ix и др.), перенесены из _DATA в _CODE (RAM).

sprinter-cc: новая опция --max-allocs N → SDCC --max-allocs-per-node
(агрессивнее аллокация регистров, меньше/быстрее код ценой времени
компиляции).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

runtime/crt0_small.s

@@ -38,6 +38,8 @@
     .globl  s__INITIALIZER
     .globl  l__INITIALIZER
     .globl  s__INITIALIZED
+    .globl  s__DATA
+    .globl  l__DATA
     .globl  s__BSS
     .globl  l__BSS
 
@@ -119,11 +121,11 @@ w2_join:
     ld    sp, #0xBFFE
 .ifdef DEBUG_RT
     ;; Save the self-alloc flag across gsinit (which clobbers BC/DE/HL and
-    ;; zeroes BSS).  SP is in W2 now, push is safe.
+    ;; zeroes _DATA/_BSS).  SP is in W2 now, push is safe.
     push  af
 .endif
 
-    ;; ----- Step 5: save IX prefix in its canonical W2 slot. -------------
+    ;; ----- Step 5: save IX prefix in its canonical slot (_CODE, W1). ----
     ld    (_estex_startup_ix), ix
 
     ;; ----- Step 6: standard gsinit + argv flow (identical to crt0.s). --
@@ -336,10 +338,13 @@ gpn_skip:
 ;; Runtime data — same layout as crt0.s.  Lives in DATA/BSS which the
 ;; linker places in W2 (--data-loc 0x8000).
 ;; =========================================================================
-    .area _DATA
+    .area _CODE
+;; _estex_startup_ix is written BEFORE gsinit runs (gsinit zeroes _DATA),
+;; so it lives in _CODE — RAM on the Sprinter, always mapped.
 _estex_startup_ix::
     .ds 2
 
+    .area _DATA
 _argc::
     .ds 2
 _argv::
@@ -362,33 +367,44 @@ _w2_self_allocated::
 .endif
 
 ;; =========================================================================
-;; gsinit — copy _INITIALIZER -> _INITIALIZED, then zero _BSS.  Identical
-;; to crt0.s; runs AFTER W2 is mapped so writes to _INITIALIZED/_BSS land.
+;; gsinit — zero _DATA + _BSS, then copy _INITIALIZER -> _INITIALIZED.
+;; Identical to crt0.s; runs AFTER W2 is mapped so the writes land.
+;; _DATA is zeroed because C guarantees zero-valued statics — initializing
+;; `static uint8_t x;` here lets code drop explicit `= 0` initializers
+;; that would otherwise burn _INITIALIZER bytes in the EXE image.
 ;; =========================================================================
-    .area _GSINIT
-gsinit::
-    ld    bc, #l__INITIALIZER
+    .area _CODE
+;; zero_area — fill BC bytes at HL with 0 (BC may be zero).
+zero_area:
     ld    a, b
     or    a, c
-    jr    Z, gsinit_bss
-    ld    de, #s__INITIALIZED
-    ld    hl, #s__INITIALIZER
-    ldir
-gsinit_bss:
-    ld    bc, #l__BSS
-    ld    a, b
-    or    a, c
-    jr    Z, gsinit_done
-    ld    hl, #s__BSS
+    ret   Z
     ld    (hl), #0
     dec   bc
     ld    a, b
     or    a, c
-    jr    Z, gsinit_done
+    ret   Z
     ld    d, h
     ld    e, l
     inc   de
     ldir
+    ret
+
+    .area _GSINIT
+gsinit::
+    ld    hl, #s__DATA
+    ld    bc, #l__DATA
+    call  zero_area
+    ld    hl, #s__BSS
+    ld    bc, #l__BSS
+    call  zero_area
+    ld    bc, #l__INITIALIZER
+    ld    a, b
+    or    a, c
+    jr    Z, gsinit_done
+    ld    de, #s__INITIALIZED
+    ld    hl, #s__INITIALIZER
+    ldir
 gsinit_done:
 
     .area _GSFINAL