v0.6.0: Clean API, chipset-keyed profiles, streamlined platform driver

- API: open() is OEM-only, wait_ready() separate, init() optional
- Profiles: chipset-keyed JSON ({ "mt1959": [...], "renesas": [] })
- Profiles: identity group, variant + signature + firmware per drive
- Platform constants: mode, buffer_id, nominal speed, verify commands
  moved from profiles to code (variant-determined, not per-drive)
- Removed unused fields: register CDBs, speed tables, status data
- Platform driver: unlock + firmware upload + calibrate + speed only
- Cross-compile fix: build.rs uses CARGO_CFG_TARGET_OS for framework linking

build.rs

@@ -1,6 +1,6 @@
 fn main() {
-    #[cfg(target_os = "macos")]
-    {
+    let target = std::env::var("CARGO_CFG_TARGET_OS").unwrap_or_default();
+    if target == "macos" {
         println!("cargo:rustc-link-lib=framework=IOKit");
         println!("cargo:rustc-link-lib=framework=CoreFoundation");
     }