Initial commit: krust - container image build tool for Rust

krust builds container images for Rust applications without Docker:
- Builds static binaries using musl libc
- Creates minimal OCI container images
- Pushes to any OCI-compliant registry
- Outputs digest to stdout for composability

Inspired by ko.build for Go applications.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

tests/integration_test.rs

@@ -0,0 +1,43 @@
+use anyhow::Result;
+use assert_cmd::Command;
+use predicates::prelude::*;
+
+#[test]
+fn test_version_command() -> Result<()> {
+    let mut cmd = Command::cargo_bin("krust")?;
+    cmd.arg("--version");
+    cmd.assert()
+        .success()
+        .stdout(predicate::str::contains("krust 0.1.0"));
+    Ok(())
+}
+
+#[test]
+fn test_version_subcommand() -> Result<()> {
+    let mut cmd = Command::cargo_bin("krust")?;
+    cmd.arg("version");
+    cmd.assert()
+        .success()
+        .stdout(predicate::str::contains("krust 0.1.0"));
+    Ok(())
+}
+
+#[test]
+fn test_help_command() -> Result<()> {
+    let mut cmd = Command::cargo_bin("krust")?;
+    cmd.arg("--help");
+    cmd.assert().success().stdout(predicate::str::contains(
+        "A container image build tool for Rust applications",
+    ));
+    Ok(())
+}
+
+#[test]
+fn test_build_help() -> Result<()> {
+    let mut cmd = Command::cargo_bin("krust")?;
+    cmd.arg("build").arg("--help");
+    cmd.assert().success().stdout(predicate::str::contains(
+        "Build a container image from a Rust application",
+    ));
+    Ok(())
+}