Sweep the pinned toolchain to Rust 1.97

The Windows UI needs current winsafe, whose real minimum is 1.89 (its manifest
under-declares 1.87 while it uses NonNull::from_ref). Rather than stop at the
minimum, this goes to current stable and fixes what that costs.

The counter-intuitive result: 1.97 is CHEAPER than 1.89. libfreemkv had 54
clippy errors at 1.89 and 6 at 1.97, because clippy tightened the noisy
collapsible_if lint in between. Stopping at the minimum would have been the most
expensive choice available.

Roughly 47 lints across the eight repos, the large majority auto-fixed:
libfreemkv 6, freemkv-engine 14, bdemu 8, freemkv-keysources 7, autorip 6,
freemkv-unlock 3, freemkv-i18n 3. The hand-fixed ones are a descending sort to
sort_by_key(Reverse), four manual checked-division sites, a loop counter replaced
by enumerate, and a loop whose first let-else became a while-let.

Worth recording for whoever bumps next: clippy is MSRV-AWARE. Those 54 lints only
appear once the crate DECLARES 1.89 or later, because let-chains become
available. A bare `cargo +1.89 clippy` against a manifest still pinned at 1.87
reports clean and is meaningless — gate with the real precommit script, which is
also the only thing that covers build scripts.

The pin still sits below the Mac default, so it keeps doing its job: catching
lint drift locally before CI sees it.

src/css/mod.rs

@@ -249,10 +249,10 @@ fn crack_key_scan(
         while i < ext.sector_count && tried < max_tries {
             // Cooperative cancellation — poll once per batch, the same cadence
             // sweep/patch use, so a Stop / watchdog can interrupt the scan.
-            if let Some(h) = halt {
-                if h.is_cancelled() {
-                    break 'outer;
-                }
+            if let Some(h) = halt
+                && h.is_cancelled()
+            {
+                break 'outer;
             }
             // Liveness beacon: a long scan over a damaged disc stays visible.
             // The heartbeat is time-throttled; only when it actually beats do
@@ -367,16 +367,16 @@ pub fn descramble_region(buf: &mut [u8], title_key: &mut [u8; 5]) {
             original.copy_from_slice(chunk);
         }
         lfsr::descramble_sector(title_key, chunk);
-        if let Some(crib) = crib {
-            if chunk[0x80..0x80 + 10] != crib[..] {
-                // Cached key is stale for this region — restore the ciphertext and
-                // crack this sector's own key.
-                chunk.copy_from_slice(&original);
-                if let Some(fresh) = stevenson::crack_title_key(chunk) {
-                    *title_key = fresh;
-                }
-                lfsr::descramble_sector(title_key, chunk);
+        if let Some(crib) = crib
+            && chunk[0x80..0x80 + 10] != crib[..]
+        {
+            // Cached key is stale for this region — restore the ciphertext and
+            // crack this sector's own key.
+            chunk.copy_from_slice(&original);
+            if let Some(fresh) = stevenson::crack_title_key(chunk) {
+                *title_key = fresh;
             }
+            lfsr::descramble_sector(title_key, chunk);
         }
     }
 }