restructure: rsnix kernel + shell crate + rsdos entry point

Architecture:
  rs-dos/  (workspace root, was raisernics/)
  ├── rsnix/     — kernel lib crate (uefi, serial, gop, ps2, interrupts, memory)
  ├── shell/     — shell lib crate (prompt, commands, line input)
  ├── rsdos/     — binary crate (efi_main, init, panic handler)
  └── rsboot/    — future git submodule

No functional changes — boots to shell prompt identically.
Version auto-pulled from Cargo.toml via env!("CARGO_PKG_VERSION").

1 files changed, 70 insertions, 0 deletions

diff --git a/rsnix/build.rs b/rsnix/build.rs
new file mode 100644
index 0000000..35447e9
--- /dev/null
+++ b/rsnix/build.rs
@@ -0,0 +1,70 @@
+/// Build script — extracts glyph data from a PSF2 font file.
+/// Uses zcat (system gzip) to decompress — zero dependencies.
+use std::env;
+use std::fs;
+use std::path::Path;
+use std::process::{Command, Output};
+
+fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let font_path = "/usr/share/kbd/consolefonts/lat1-16.psfu.gz";
+    println!("cargo::rerun-if-changed={}", font_path);
+
+    // Decompress via zcat (available on any Linux system)
+    let Output { stdout, status, .. } = Command::new("zcat").arg(font_path).output()?;
+    if !status.success() {
+        return Err(format!("zcat exited with {status:?}").into());
+    }
+    let raw = stdout;
+
+    if raw.len() < 32 {
+        return Err("PSF font too small".into());
+    }
+
+    // PSF2 magic: 0x864ab572 (little-endian)
+    let magic = u32::from_le_bytes(raw[..4].try_into()?);
+    if magic != 0x864ab572 {
+        return Err("not a PSF2 font".into());
+    }
+
+    let hdr_size = u32::from_le_bytes(raw[8..12].try_into()?) as usize;
+    let num_glyphs = u32::from_le_bytes(raw[16..20].try_into()?) as usize;
+    let bytes_per_glyph = u32::from_le_bytes(raw[20..24].try_into()?) as usize;
+
+    if num_glyphs != 256 {
+        return Err(format!("expected 256 glyphs, got {num_glyphs}").into());
+    }
+    if bytes_per_glyph != 16 {
+        return Err(format!("expected 16 bytes/glyph, got {bytes_per_glyph}").into());
+    }
+
+    let glyph_data = &raw[hdr_size..hdr_size + num_glyphs * bytes_per_glyph];
+
+    // Write generated Rust source into OUT_DIR
+    let out_dir = env::var("OUT_DIR")?;
+    let dest = Path::new(&out_dir).join("font_data.rs");
+
+    let mut code = String::from(
+        "/// 8×16 bitmap font glyph data (256 glyphs, 16 bytes each).
+#[rustfmt::skip]
+#[allow(clippy::unreadable_literal)]
+pub const GLYPH_8X16: [[u8; 16]; 256] = [",
+    );
+
+    for g in 0..256 {
+        let offset = g * 16;
+        code.push_str("\n    [");
+        for row in 0..16 {
+            if row % 4 == 0 {
+                code.push('\n');
+            }
+            let byte = glyph_data[offset + row];
+            code.push_str(&format!(" 0x{byte:02X},"));
+        }
+        code.push_str("\n    ],");
+    }
+
+    code.push_str("\n];\n");
+
+    fs::write(&dest, code)?;
+    Ok(())
+}