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>

third_party/solid-c/SRC/CLIB/STARTUP.ASM

@@ -0,0 +1,68 @@
+;///////////////////////////////////////////////////////////////////////////
+;
+;		C LIBRARY FOR SOLID C compiler
+;			Root module
+;
+;///////////////////////////////////////////////////////////////////////////
+
+; ‚室ï騥 ä㭪樨:
+;
+; xmain
+; _exit
+; abort
+;
+
+
+
+	cseg
+
+	db	"CLIB v0.01",0
+
+
+xmain::
+	; ᮧ¤ âì ᯨ᮪  à£ã¬¥­â®¢
+	push	ix
+	pop	hl			;  ¤à¥á ª®¬. áâப¨
+	call	_setargv##		; ¢ dos.asm
+	ld	de,_argv_##		; ᯨ᮪  à£ã¬¥­â®¢ (¢ dos.asm)
+
+	call	_main_##		; ¢ stdio.asm
+
+;
+; "stdlib.h"
+; ¯¥à¥¤ ¥âáï ã¯à ¢«¥­¨¥ ¨§ ä㭪樨 exit.
+; ”ã­ªæ¨ï § ¢¥à蠥⠢맢 ­­ë© ¯à®æ¥áá ¡¥§ ®¡­®¢«¥­¨ï ¡ãä¥à®¢ ¯®â®ª .
+; ‡­ ç¥­¨¥ code ®¡ëç­® ãáâ ­ ¢«¨¢ ¥âáï ¢ 0 ¤«ï 㪠§ ­¨ï ­®à¬ «ì­®£®
+; ¢ë室  ¨ ãáâ ­ ¢«¨¢ ¥âáï ¢ «î¡®¥ ¤à㣮¥ §­ ç¥­¨¥ ¤«ï ®¯à¥¤¥«¥­¨ï ®è¨¡ª¨.
+; �®áª®«ìªã ¢ë§®¢ _exit ­¥ ¢®§¢à é ¥â §­ ç¥­¨ï, â® ¬«. ¡ ©â code ï¥âáï
+; ª®¤®¬ ¢®§¢à â  ¤«ï த¨â¥«ì᪮£® ¯à®æ¥áá .
+; in: hl = §­ ç¥­¨¥ error code
+; out: ­¥â
+;
+; void _exit(int code)
+;
+_exit_::
+	ld	b,l
+	ld	c,41h		; terminate with error code
+	rst	10h
+	ret
+
+;
+; "stdlib.h"
+; ”ã­ªæ¨ï ¢ë¢®¤¨â ­  íªà ­ á®®¡é¥­¨¥ "Abnormal program termination."
+; (­¥¯à¥¤¢¨¤¥­­®¥ § ¢¥à襭¨¥ ¯à®£à ¬¬ë) ¨ § ¢¥à蠥⠢맢 ­­ë© ¯à®æ¥áá
+; ¡¥§ ®¡­®¢«¥­¨ï ¡ãä¥à®¢ ¯®â®ª .
+; in: ­¥â
+; out: ­¥â
+;
+; void abort()
+;
+abort_::
+	ld	hl,@1
+	ld	c,5Ch
+	rst	10h
+	ld	l,-1
+	jr	_exit_
+
+	dseg
+@1:	db	0Dh,0Ah,"Abnormal program termination.",0Dh,0Ah,0Ah,0