libc review: mem/, stdio/, fixes in sprinter-cc and FILE shim

libc/mem/:
  • Split bank_io.c into bank_io_w3.c (existing W3 helpers, base 0xC000,
    port 0xE2) and bank_io_w1.c (new mirror through W1, base 0x4000,
    port 0xA2).  Two .rel files so DCE picks only the needed group:
    a W3-only user pulls ~70 bytes instead of all 134.  W1 variants are
    `--memory tiny`-only (any other mode runs code from W1 or uses W1
    for the banked-code segment, swapping it crashes).
  • mem_alloc.c: add CF=err checks for mem_free_block and mem_get_page
    (were silently ignored), per-function docstrings on alloc/free/
    get_page/info, drop the confused "wait wrong order" comment in
    mem_info.  Header sprinter_mem.h gets matching per-function doc.

libc/stdio/:
  • Add hex_print.c (hex8/hex16/hex32, ~26 bytes) and dec_print.c
    (dec8/dec16/dec32, ~170 bytes) ported from solid-c STDLIB.ASM.
    Replaces the printf("%u"/"%X") wrappers in solid_helpers.c that
    dragged in the 3-5 KB printf machinery.
    - hex* use the classic cp 10 / sbc 0x69 / daa nibble→ASCII trick;
      hex8 self-calls for the high nibble, hex16/hex32 tail-call hex8.
    - dec32 is the master routine; dec8/dec16 jump into shared entry
      points (__dec_entry3 / __dec_entry5).  32-bit subtract-power-of-10
      keeps the high 16 bits in HL alt (shadow set).
    - DISCOVERY: ESTEX PUTCHAR ($5B) on our Sprinter build preserves
      the main register set + IX but CLOBBERS the shadow set
      (BC'/DE'/HL').  solid-c's original code assumed otherwise and
      garbled output for values ≥ 6 digits.  Fix: save/restore HL alt
      around the RST 10 in _dec_emit_or_skip.  Documented in
      memory/estex_putchar_abi.md.
  • file.c: drop stdaux/stdprn (no Sprinter printer API), change
    stdin/stdout/stderr fd markers to 0/-1/-2 (positive fds clash with
    ESTEX OPEN return values), add TODO header pointing at v2 buffered
    FILE rewrite (see docs/TODO.md for the Solid-C reference struct).

bin/sprinter-cc:
  • --memory big and --memory huge now always use crt0_banked.s (was:
    only with --bank flags), matching docs/memory_modes_implemented.md.
    When the user has no --bank flags, generate a tiny stub with
    `const uint8_t n_banks = 0;` and assemble bank.s for _bank_pages.
    Without this fix, openenv with --memory big could not see the
    estex_file_handle symbol exported by crt0_banked.

examples/openenv:
  • Add usage of estex_file_handle to confirm the crt0_banked startup-
    info is reachable.  Local extern decl — keeps the symbol out of
    sprinter.h since it only exists in big/huge builds.

examples/dec_test:
  • New regression test covering hex8/16/32 and dec8/16/32 across the
    interesting boundary values.

.gitignore: add .kilo/ (editor session cache).

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

README.md

@@ -51,13 +51,13 @@ Sprinter's address space is four 16 KB windows (W0 / W1 / W2 / W3).  DSS allocat
 pages by program size — small programs get only one page.  Pick a memory mode based
 on what your program needs:
 
-| Mode | Code lives in | Banking | Use when |
+| Mode | Code lives in | Banking | Use when | Note |
 |---|---|---|---|
-| `tiny`  (default) | W2 (0x8100+) | no | code+data < 14 KB |
-| `small` | W1 (0x4100+) | no | code+data < 30 KB |
-| `big`   | W2 + W1 banks | yes (W1) | tiny + extra code modules |
-| `huge`  | W1 + W3 banks | yes (W3) | small + extra code modules |
-| `manual` | user-specified | optional | special layouts |
+| `tiny`  (default) | W2 (0x8100+) | no | code+data < 14 KB | |
+| `small` | W1-W2 (0x4100+) | no | code+data < 30 KB | |
+| `big`   | W2 + W1 banking | yes (W1) | tiny + extra code modules | |
+| `huge`  | W1-W2 + W3 banking | yes (W3) | small + extra code modules | |
+| `manual` | user-specified | optional | special layouts | Not implemented |
 
 ```sh
 sprinter-cc --memory small  -o big.exe   bigprog.c
@@ -157,20 +157,24 @@ sprinter-cc -o foo.exe foo.c [more.c ...] [options]
 
 What works in v1.0:
 * Compile / link / pack to SprintEXE — verified on all 27 examples
-* All five memory modes (tiny / small / big / huge / manual)
+* Four memory modes (tiny / small / big / huge)
 * Graphics (both modes) with accelerator
 * Mouse (text + graphics cursor)
 * File I/O, directories, environment, time
 * All headers listed above
 
 Deferred to v2.0 (see `docs/TODO.md`):
-* **IM2 interrupt handlers** — research complete (`docs/im2_isr_design.md`),
-  implementation scheduled for v2
 * **Turbo-C-style BGI graphics API** — `initgraph` / `setcolor` / `circle` /
   `getimage` / `putimage` / etc. on top of our `gfx_*` primitives
-* **Audio API** (AY-3-8910 + COVOX) — requires IM2
-* **ISA-8 slot drivers** — requires IM2
 * Remaining Solid-C compatibility gaps (Phase 2/3) — see `docs/solid_c_compatibility.md`
+* Manual memory mode
+* Rewrite FILE\* stream API (current implementation is very primitive and doesn't use buffers)
+
+Deferred to v3.0:
+* **IM2 interrupt handlers** — research complete (`docs/im2_isr_design.md`),
+  implementation scheduled for v3
+* **Audio API** (AY-3-8910 + COVOX) — requires IM2
+* **ISA-8 slot drivers** — requires IM2 (???)
 
 ## Documentation