Refactor: Chipset architecture, remove supported/status gatekeeping

- PlatformType → Chipset enum (MediaTek, Renesas)
- unlock_mode + unlock_buf_id stored in profile, not derived from enum
- Removed ReadinessStatus, supported field, needs_flash — library is agnostic
- Removed DriveMatch/Flashable — if we have a profile, try unlock
- profiles.json: chipset + unlock_mode + unlock_buf_id, no program/supported
- mt1959.rs reads mode/buf_id from profile fields directly
- Tests: find_known_drive, find_unknown_drive

src/platform/mt1959.rs

@@ -25,8 +25,8 @@ pub struct Mt1959 {
 
 impl Mt1959 {
     pub fn new(profile: DriveProfile) -> Self {
-        let mode = profile.platform.mode();
-        let buffer_id = profile.platform.buffer_id();
+        let mode = profile.unlock_mode;
+        let buffer_id = profile.unlock_buf_id;
         Mt1959 {
             profile,
             mode,