feat: system config DSL, services, CLI with rustc diagnostics

- System config parser (system/packages/services/boot/users blocks)
- Boot block: kernel, init, efi, swap, bootloader, root partition
- System-wide features, rollback config, swap partition
- Service block: per-init variants (runit, s6, etc.), system init selection via boot.init
- Feature-gated dependencies, config values accept numbers/bools/strings
- CLI: parse-package, parse-config, validate subcommands
- Rustc-style error diagnostics with source context, carets, help text
- Diagnostic module with ANSI color output

examples/config.kap

@@ -0,0 +1,87 @@
+/*
+ * Kappa system configuration.
+ * Lives at /kappa/system/config.kap
+ */
+system {
+    hostname = "kappa.local"
+    timezone = "America/New_York"
+
+    features {
+        ssl         = true
+        wayland     = false
+        pulseaudio  = false
+    }
+
+    env {
+        CFLAGS    = "-O2 -march=native"
+        LDFLAGS   = "-Wl,--as-needed"
+        MAKEFLAGS = "-j8"
+    }
+
+    config {
+        prefix  = "/usr"
+        log_dir = "/var/log"
+    }
+
+    rollback {
+        keep = 5
+    }
+}
+
+packages {
+    foo {
+        version = ">=1.2"
+        features {
+            gui = true
+        }
+        config {
+            port = "9090"
+            ssl  = true
+        }
+    }
+    bar {}
+    baz {
+        features {
+            ssl = false
+        }
+    }
+
+    /*
+    // Per-package overrides can also live in
+    // /kappa/system/builds/<name>.kap
+    */
+}
+
+services {
+    nginx {
+        enable = true
+        port   = 80
+        ssl    = true
+    }
+    sshd {
+        enable = true
+        port   = 22
+    }
+    cron {
+        enable = false
+    }
+}
+
+boot {
+    kernel     = "linux"
+    init       = "s6"
+    efi        = "/dev/sda2"
+    swap       = "/dev/sda3"
+    bootloader = "limine"
+    root       = "/dev/sda1"
+}
+
+users {
+    specter {
+        shell  = "/bin/zsh"
+        groups = ["wheel", "audio", "docker"]
+    }
+    root {
+        shell = "/bin/zsh"
+    }
+}

examples/foo.kap

@@ -59,6 +59,20 @@ package "foo" {
         CFLAGS  ?= "-g"
     }
 
+    service {
+        runit {
+            exec  = "/usr/bin/foo --daemon"
+            type  = "forking"
+            user  = "foo"
+        }
+        s6 {
+            exec  = "/usr/bin/foo"
+            type  = "longrun"
+            ports = [80, 443]
+            user  = "foo"
+        }
+    }
+
     prepare {
         patch "fix-build.patch"
     }