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>

Makefile

@@ -0,0 +1,88 @@
+# Sprinter C Compiler — top-level Makefile
+#
+#   make             build host tools, libc archive, and all examples
+#   make tools       build only host tools (mkexe)
+#   make lib         build lib/sprinter.lib (libc archive used by sprinter-cc)
+#   make examples    build all examples
+#   make floppy      package every example + test files into mame/v306/IMG/mc.img
+#   make check       run mkexe unit tests
+#   make clean       remove all build artefacts
+#   make sdcc        download/extract vendored SDCC
+#
+# Most heavy lifting is delegated to sub-Makefiles.
+
+EXAMPLES := hello banked bankedbg strtest cat seek malloc mem_test argv errno rt_test openenv ls conio attrprob timedir mouse banklocl stdlib assrtest ptime stattest filetest gfx_demo gfx_d16 gfx_text gfx_mous
+
+MAME_DIR    := mame/v306
+FLOPPY_IMG  := $(MAME_DIR)/IMG/mc.img
+MAKE_DISK   := $(MAME_DIR)/make_disk.py
+
+EXE_FILES := \
+    examples/hello/hello.exe       \
+    examples/banked/banked.exe     \
+    examples/bankedbg/bankedbg.exe \
+    examples/strtest/strtest.exe   \
+    examples/cat/cat.exe           \
+    examples/seek/seek.exe         \
+    examples/malloc/malloc.exe     \
+    examples/mem_test/mem_test.exe \
+    examples/argv/argv.exe         \
+    examples/errno/errno.exe       \
+    examples/rt_test/rt_test.exe   \
+    examples/openenv/openenv.exe   \
+    examples/ls/ls.exe             \
+    examples/conio/conio.exe       \
+    examples/attrprob/attrprob.exe \
+    examples/timedir/timedir.exe   \
+    examples/mouse/mouse.exe       \
+    examples/banklocl/banklocl.exe \
+    examples/stdlib/stdlib.exe     \
+    examples/assrtest/assrtest.exe \
+    examples/ptime/ptime.exe       \
+    examples/stattest/stattest.exe \
+    examples/filetest/filetest.exe \
+    examples/gfx_demo/gfx_demo.exe \
+    examples/gfx_d16/gfx_d16.exe   \
+    examples/gfx_text/gfx_text.exe \
+    examples/gfx_mous/gfx_mous.exe
+
+DATA_FILES := \
+    examples/cat/test.txt          \
+    examples/seek/big.txt
+
+.PHONY: all tools lib examples check clean sdcc floppy $(EXAMPLES)
+
+all: tools lib examples
+
+tools:
+	$(MAKE) -C toolchain/mkexe
+
+lib:
+	$(MAKE) -C lib
+
+check: tools
+	$(MAKE) -C toolchain/mkexe check
+
+examples: $(EXAMPLES)
+
+$(EXAMPLES): tools lib
+	$(MAKE) -C examples/$@
+
+# Generate big.txt if missing (gen_bigfile.py creates 100 KB marker file).
+examples/seek/big.txt:
+	cd examples/seek && python3 gen_bigfile.py big.txt 102400
+
+# Re-pack the MAME floppy image with every built example + needed data files.
+floppy: examples examples/seek/big.txt
+	python3 $(MAKE_DISK) $(FLOPPY_IMG) $(EXE_FILES) $(DATA_FILES)
+	@echo
+	@echo "Floppy ready: $(FLOPPY_IMG)"
+	@echo "Run:  cd $(MAME_DIR) && ./run_mame.sh"
+
+clean:
+	$(MAKE) -C toolchain/mkexe clean
+	$(MAKE) -C lib clean
+	@for e in $(EXAMPLES); do $(MAKE) -C examples/$$e clean; done
+
+sdcc:
+	bash third_party/setup-sdcc.sh