Fix rc5 audit findings: keydb doc, pipeline ordering, hot-loop Arc, tests

- keydb.rs: separate default_path()/no_home_dir() doc blocks; correct the
  false XDG lock-step claim (Linux write path uses $HOME, ignores
  XDG_CONFIG_HOME; read-side search also checks XDG_CONFIG_HOME).
- io/pipeline.rs: use Release/Acquire on the abandoned flag so a leaked
  consumer reliably skips close() on weak memory models (ARM64/POWER),
  not just x86 TSO.
- mux/disc.rs: cache the decrypt-loss Arc at construction; lost_bytes()
  no longer clones an Arc per frame on the mux hot path.
- disc/dvd.rs: assert display_aspect mapping for both 16:9 (PAL test) and
  4:3 (NTSC test).
- mux/resolve.rs: extract css_error_aborts() helper and unit-test the
  scrambled-but-uncracked CSS guard (Fix 6) incl. the --raw exemption.
- aacs/keys.rs: add unit tests for mkb_type_raw/mkb_type/mkb_is_uhd and
  MkbType (Category C 2.0 UHD, prerecorded 1.0, no-0x10-record None).
- release.yml: publish job needs [verify, test] so a failing test suite
  blocks crates.io publication.

src/io/pipeline.rs

@@ -150,7 +150,11 @@ fn finish_with_grace<R: Send + 'static>(
     // observes it the moment its wedged syscall returns: it then skips
     // any further `apply` and skips `close()`, rather than running on to
     // finalise the abandoned output file.
-    abandoned.store(true, Ordering::Relaxed);
+    // `Release` here pairs with the `Acquire` loads in the consumer loop so
+    // the leaked consumer reliably observes the flag the moment its wedged
+    // syscall returns, even on weak memory models (ARM64/POWER) where
+    // `Relaxed` gives no cross-thread visibility guarantee.
+    abandoned.store(true, Ordering::Release);
     tracing::warn!(
         target: "freemkv::pipeline",
         phase = "finish_with_halt_grace_expired",
@@ -299,7 +303,7 @@ impl<I: Send + 'static, R: Send + 'static> Pipeline<I, R> {
                     // dead receiver, but we touch the output no further. The
                     // final post-loop abandonment check returns the error
                     // and skips `close()`.
-                    if abandoned_consumer.load(Ordering::Relaxed) {
+                    if abandoned_consumer.load(Ordering::Acquire) {
                         continue;
                     }
 
@@ -359,7 +363,7 @@ impl<I: Send + 'static, R: Send + 'static> Pipeline<I, R> {
                 // MKV Cues + patching the segment header) on a file the
                 // caller already reported as failed is exactly the
                 // write race we must not run.
-                if abandoned_consumer.load(Ordering::Relaxed) {
+                if abandoned_consumer.load(Ordering::Acquire) {
                     return Err(Error::Halted);
                 }