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>

libc/include/mouse.h

@@ -0,0 +1,113 @@
+/*
+ * mouse.h — Sprinter mouse driver (RST 30h).
+ *
+ * The driver is installed in the system shell.  After a successful
+ * mouse_init(), the driver tracks the hardware and you can query state
+ * or move/show/hide the cursor on demand.
+ *
+ *   coordinate units:
+ *     READ_STATE / GOTO take pixel coordinates.  In text mode 03h
+ *     (80x32) divide x by 8 and y by 8 (NOT 16) to get char-cell
+ *     position.
+ *
+ *   buttons bitmask:
+ *     bit 0 = left, bit 1 = right
+ */
+
+#ifndef MOUSE_H
+#define MOUSE_H
+
+#include <stdint.h>
+
+typedef struct {
+    uint16_t x;        /* pixel coordinate */
+    uint16_t y;        /* pixel coordinate */
+    uint8_t  buttons;  /* bit 0 = left, bit 1 = right */
+} mouse_state_t;
+
+int  mouse_init   (void);                       /* 0 OK, -1 if no driver */
+void mouse_show   (void);
+void mouse_hide   (void);
+void mouse_refresh(void);
+void mouse_read   (mouse_state_t *st);
+void mouse_goto   (int x, int y);
+void mouse_bounds_x(int xmin, int xmax);
+void mouse_bounds_y(int ymin, int ymax);
+
+/* Text-mode cursor shape (function $0A).
+ *   sym_and / sym_xor — character glyph mask
+ *   attr_and / attr_xor — attribute byte mask
+ * Default cursor is XOR'd inverse video at the cell. */
+void mouse_text_cursor(uint8_t sym_and, uint8_t sym_xor,
+                       uint8_t attr_and, uint8_t attr_xor);
+
+/* ---- Graphics-mode cursor image (functions $09 / $0B) ----------- *
+ * The driver accepts an opaque bitmap for the cursor in graphics modes.
+ * Doc does not specify the byte layout — empirically size = width*height
+ * bytes (1 byte per pixel for 256-colour mode, presumably packed nibbles
+ * for 16-colour mode).  hot_x / hot_y mark the "click point" within the
+ * cursor image (0,0 = top-left).
+ */
+typedef struct {
+    const void *image;   /* bitmap data */
+    uint8_t     width;
+    uint8_t     height;
+    uint8_t     hot_x;
+    uint8_t     hot_y;
+} mouse_cursor_t;
+
+void mouse_load_cursor(const mouse_cursor_t *c);
+
+/* Read back the current cursor.
+ *   c->image must point to a buffer large enough to hold width*height bytes.
+ *   width, height, hot_x, hot_y are written by the driver. */
+void mouse_get_cursor(mouse_cursor_t *c);
+
+/* ---- Sensitivity (functions $0E / $0F) ------------------------- *
+ * Verified empirically (2026-05-31): the value is a DIVIDER — the
+ * driver counts that many raw hardware steps from the mouse before
+ * advancing the cursor by one screen pixel.  So **smaller value = more
+ * sensitive** (cursor moves faster), and larger value = slower cursor.
+ * (The doc statement "higher = less movement needed" appears to be
+ * inverted.)  Useful starting point: 2 on both axes. */
+uint8_t mouse_get_sensitivity_x(void);
+uint8_t mouse_get_sensitivity_y(void);
+void    mouse_set_sensitivity(uint8_t horz, uint8_t vert);
+
+/* ---- Solid-C compatibility ------------------------------------- *
+ * Solid-C uses shorter `ms_*` names + typed state structs.  The semantics
+ * are identical to our `mouse_*` API. */
+
+#define LEFT_BUTTON   1
+#define RIGHT_BUTTON  2
+
+/* MSGSTAT mirrors mouse_state_t — same field order and types. */
+typedef mouse_state_t MSGSTAT;
+
+#define ms_init       mouse_init
+#define ms_show       mouse_show
+#define ms_hide       mouse_hide
+#define ms_ref        mouse_refresh
+#define ms_xbnd       mouse_bounds_x
+#define ms_ybnd       mouse_bounds_y
+#define ms_spos       mouse_goto
+#define mssgpos       mouse_goto
+#define ms_tcur       mouse_text_cursor
+#define ms_scur       mouse_load_cursor
+#define ms_gcur       mouse_get_cursor
+#define ms_vmod       mouse_video_mode_changed
+#define ms_ssen       mouse_set_sensitivity
+#define msgstat(st)   mouse_read((st))
+
+/* ---- $81 CHANGE VIDEO MODE ------------------------------------- *
+ * Call after changing the video mode (set_videotextmode or gfx_init) so
+ * the driver re-syncs its internal coordinate ranges and cursor image.
+ *
+ * `mode` is the byte you switched to — TEXT_MODE_* (from <conio.h>) or
+ * GFX_MODE_* (from <gfx.h>), e.g. 0x03 for 80×32 text or 0x81 for
+ * 320×256×256.  The driver REQUIRES the new mode in register A —
+ * passing garbage leaves the cursor mis-configured (text-mode XOR
+ * pattern applied in graphics, etc.). */
+void mouse_video_mode_changed(uint8_t mode);
+
+#endif