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/mux/codec/vc1.rs

@@ -216,12 +216,11 @@ impl CodecParser for Vc1Parser {
                         let end = find_next_sc(data, i + 4).unwrap_or(data.len());
                         let sh = &data[i..end];
                         // Try to parse resolution from advanced profile sequence header
-                        if self.seq_header.is_none() {
-                            if let Some((w, h)) = parse_vc1_resolution(sh) {
+                        if self.seq_header.is_none()
+                            && let Some((w, h)) = parse_vc1_resolution(sh) {
                                 self.width = w;
                                 self.height = h;
                             }
-                        }
                         // Collect into a scratch Vec so handle_header can
                         // append; we discard the Vec and only keep the flag.
                         let mut scratch = Vec::new();
@@ -250,12 +249,11 @@ impl CodecParser for Vc1Parser {
                         }
                         has_entry_point = true;
                     }
-                    SC_FRAME => {
+                    SC_FRAME
                         // Frame data starts at this start code
-                        if frame_start.is_none() {
+                        if frame_start.is_none() => {
                             frame_start = Some(i);
                         }
-                    }
                     _ => {}
                 }
                 i += 4;