Add full compiler toolchain, libc, examples and reference docs

First substantive commit: the entire Sprinter C compiler tree on top of
the bare README+gitignore initial commit.

What's in here:
  bin/sprinter-cc        — driver script invoking SDCC + linker + mkexe
  libc/                  — Sprinter-specific libc layer over ESTEX/BIOS
                           (conio, gfx, io, mem, stdio + headers)
  runtime/               — crt0 variants (default/small/banked/minimal)
                           + heap + bank trampolines
  toolchain/             — mkexe (SprintEXE packer, C + tests)
  examples/              — 30 demo programs (gfx, file I/O, env, time, …)
  lib/Makefile           — builds the libc archive (sprinter.lib)
  docs/                  — converted Sprinter manuals + asm reference samples
  third_party/           — solid-c reference compiler dump + sdcc setup script
  release_docs/          — packaging / release notes

gitignore overhaul:
  • Drop dangerous blanket patterns: *.asm (would hide docs/samples/*.asm)
    and *.exe (case-insensitive match was hiding third_party/solid-c/*.EXE
    on macOS APFS).  Replaced with examples/*/*.{asm,exe,…} and lib/*.lib.
  • Restore tracking of toolchain/mkexe/tests/{one,big}.bin — those are
    INPUT fixtures, not build outputs.
  • Collapse the duplicated SDCC/C/Sdcc sections into one section per
    concern (build outputs / vendored / OS-junk).
  • Add .sprinter-cc-*/, build/ (catches lib/build/ too), .claude/.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

docs/reference/SPRINT2K/sprn2k76.txt

@@ -0,0 +1,84 @@
+*** Area: ZX.SPECTRUM                             Date: 18 Jun 03  7:19:58
+*** From: Kirill Frolov (2:5030/827.2)
+*** To  : Alexander Ryabov
+*** Subj: � §«¨ç­ë¥ ¯p®¥ªâë ¤«ï ZX
+
+H¥¬¥¤«¥­­® ­ ¦¬¨ ­  RESET, Alexander Ryabov!
+
+On Tue, 17 Jun 03 18:50:52 +0400, Alexander Ryabov wrote:
+
+ AR> �¥ «ì­® ¯®«ãç¨âì ¨­ä®à¬ æ¨î ® á¯2000 ¢ �¨â¥à¥ - ¨¤â¨ ¢ �¥â¥àá?
+
+   Œ®¦¥èì ¨¤â¨ ­  http://www.petersplus.com.
+ 
+ AR> Œ®¦¥â ¡ëâì, ¤¥©á⢨⥫쭮 ®¯ã¡«¨ª®¢ âì ¢ íå¥?
+
+   € á¬ëá«?  ‘® ᯥªâà㬮¬ ®­® ­¥ ᮢ¬¥á⨬®, ¤®á â ¬ ᢮©...
+H¥¤®¯¨áîª ­¥¯®­ïâ­ë© :-/
+ 
+ AR> ‘ª®«ìª® ¢¥áïâ ⥪áâë?
+
+   ‘ª ç « Sprinter-SDK. ‚­ãâਠsetup.exe ä ©« á â ª¨¬:
+
+    ’his program must be run under Win32
+
+  H¥ ¨­ ç¥ ª ª Win32 ­  á¯à¨­â¥à ¯®àâ¨à®¢ «¨...
+
+  setup.exe í⮠® ¢à¥¤®­®á­ ï ¯à®£à ¬¬ ... (ã ¬¥­ï windows'a ­  C: ­¥â!)
+SDK ®ª § «®áì ⥪áâ®¢ë¬ à¥¤ ªâ®à®¬ ¤«ï ¢¨­¤®¢á (­  á¯à¨­â¥à¥ ­ ¢¥à­®¥ ­¥
+§ ¯ã᪠¥âáï) á ª­®¯ª®© ¤«ï ¯ã᪠ rw1p ª®¬¯¨«ïâ®à  (íâ® â ª®© ­¥¤® áᥬ¡«¥à).
+H¨ª ª¨å ¤®ª®¢ ®ªà®¬ï readme â ¬ ­¥¡ë«®. H  㯮¬ï­ã⮬ ¢ëè¥ http ⮦¥
+ª ª-â® ­¥ ®á®¡® § ¬¥â­®.
+ 
+ AR> ‘ª ¦¥¬, ¯®«ãç¨âì ¢áî ®âªàëâãî ¤®ªã¬¥­â æ¨î ­¥ âॡã¥âáï -
+ AR> ­® à §¢¥à­ã⮥ ®¯¨á ­¨¥ 2000£® á¯à¨­â¥à ,   ®â á¯à¨­â¥à97 ®­, ¢¨¤¨¬®,
+ AR> ¤®áâ â®ç­® ᨫ쭮 ®â«¨ç âáï(?), ­ã¦­®.
+
+  �â® ¢áñ çâ® ï ­ èñ« ­  http://www.sprinter.com
+(¬®¦¥â â ¬ £¤¥-â® çâ®-â® ¥áâì, ­® ᮮ⢥âáâ¢ãîéãî áá뫪ã á¯àïâ «¨ å®à®è®)
+
+Š®¬¯ìîâ¥à Sprinter
+“­¨¢¥àá «ì­ë© ª®¬¯ìîâ¥à Sprinter ­  ¡ §¥ ¯à®æ¥áá®à  Z80 ª®à¯®à æ¨¨ Zilog.
+
+- ƒ¨¡ª ï  àå¨â¥ªâãà 
+- �« â  Sp2000s áâ ­¤ àâ­ë© ª®¬¯«¥ªâ
+- — áâ®â  ¯à®æ¥áá®à  21MHz
+- Ž‡“ - 4 Mb
+- ‚¨¤¥® ¢ë室 - ’¥«¥¢¨§®à ¨«¨  ­ «®£®¢ë© CGA ¬®­¨â®à
+- ‚¨¤¥® ०¨¬ë: 320x256, 256 梥⮢, 640x256, 16 梥⮢
+- � «¨âà  16 ¬«­. 梥⮢
+- ’¥ªáâ®¢ë© à¥¦¨¬: 80x32 ᨬ¢®«®¢
+- €¯¯ à â­ë© ã᪮à¨â¥«ì ®¯¥à æ¨© á Ž‡“
+- 16 ¡¨â­ë© §¢ãª
+- �¥¦¨¬ ᮢ¬¥á⨬®á⨠á ZX Spectrum
+> USD $169
+
+Sp2000s (‘â ­¤ àâ­ë© ª®¬¯«¥ªâ)
+Š®¬¯ìîâ¥à­ ï ¯« â  Sp2000s, ࠧࠡ®â ­­ ï ¤«ï ª®¬¯ìîâ¥à  Sprinter ¢ 2003 £®¤ã.
+- �à®æ¥áá®à Z84C15 ( 21MHz / 3.5MHz)
+- Ž‡“ (72 pin SIMM, 7MHz) - 4Mb (à áè¨àï¥âáï ¤® 64 Mb)
+- ‚¨¤¥® Ž‡“ - 512Kb
+- �‡“ (BIOS) - 256Kb
+- ��‹Œ (ALTERA Corp.) - EP1K30QC208-3
+- Š®­â஫«¥àë - IDE & FDD
+- ‘«®âë - ¤¢  ISA-8
+- ‡¢ãª®¢®© –€� - 16 ¡¨â áâ¥à¥®
+> USD $128
+
+VGA Converter
+‚¨¤¥® ¤ ¯â¥à RGB->VGA, ࠧࠡ®â ­­ë© ¤«ï ª®¬¯ìîâ¥à  Sprinter.
+
+- 75Hz ¢¥à⨪ «ì­®© ç áâ®âë
+- ISA-8 ᮢ¬¥á⨬ ï ª àâ 
+- 8Mb SD-RAM
+- �‹Œ EP1K30QC208-3 (ALTERA Corp.)
+- 8-b ¡¨â­ë¥ €–� ¨ –€�
+
+
+ AR> ‚®¯à®áë ¬®£ãâ ¯®ï¢¨âìáï ¯®â®¬ - ¯® ¬¥à¥ ®§­ ª®¬«¥­¨ï.
+
+   ‘ã¤ï ¯® ¢á¥¬ã, ¯à¨­æ¨¯¨ «ì­ëå ®â«¨ç¨© ¢ ¦¥«¥§¥ Sprinter2K ¨ Sprinter97
+­¥ ¨¬¥îâ.  
+
+--- [ZX]
+ * Origin: ­  ¯æ ¬ë áâ ¢¨¬ ªà¥áâ, speccy ¯®ª®«¥­ì¥ next! (2:5030/827.2)