feat: initial implementation of Depot package manager

- Implement source-based package management with support for archives and Git
- Add multi-system build support (Autotools, CMake, Meson, Rust/Cargo, Custom)
- Implement atomic installation logic using transactions and fakeroot
- Add dependency resolution for build-time and runtime requirements
- Implement package indexing and local repository management
- Add comprehensive configuration system with system/package overrides
- Include Project guidelines (AGENTS.md) and README.md

src/builder/bin.rs

@@ -0,0 +1,42 @@
+//! Binary package "build" system — used when package supplies a prebuilt binary installer
+
+use anyhow::{Context, Result};
+use std::fs;
+use std::os::unix::fs as unix_fs;
+use std::path::Path;
+use walkdir::WalkDir;
+use crate::package::PackageSpec;
+use crate::cross::CrossConfig;
+
+/// For binary packages we simply copy the extracted files into DESTDIR (preserving
+/// directory structure). This is useful for .deb packages where extract step
+/// already unpacked the data payload into the source directory.
+pub fn build(
+    _spec: &PackageSpec,
+    src_dir: &Path,
+    destdir: &Path,
+    _cross: Option<&CrossConfig>,
+) -> Result<()> {
+    println!("Binary install: copying files from {} to {} (pkg type={})", src_dir.display(), destdir.display(), _spec.build.flags.binary_type);
+    fs::create_dir_all(destdir).with_context(|| format!("Failed to create destdir: {}", destdir.display()))?;
+
+    for entry in WalkDir::new(src_dir) {
+        let entry = entry?;
+        let rel = entry.path().strip_prefix(src_dir).unwrap();
+        let target = destdir.join(rel);
+        if entry.file_type().is_dir() {
+            fs::create_dir_all(&target)?;
+        } else if entry.file_type().is_symlink() {
+            let link_target = fs::read_link(entry.path())?;
+            if let Some(parent) = target.parent() { fs::create_dir_all(parent)?; }
+            // overwrite existing links/files
+            if target.exists() { let _ = fs::remove_file(&target); }
+            unix_fs::symlink(link_target, &target)?;
+        } else {
+            if let Some(parent) = target.parent() { fs::create_dir_all(parent)?; }
+            fs::copy(entry.path(), &target)?;
+        }
+    }
+
+    Ok(())
+}