Round 3: fix three defects introduced by the round-2 fixes

Auditing my own fixes found all three. None were in the original code.

The VTS crack sort was byte-wise case-SENSITIVE while the filters that select
those files (vts_group_of / is_title_vob) are case-insensitive. On a
case-sensitive volume a set holding vts_01_1.vob beside VTS_01_2.VOB sorted
part 2 first, because V (0x56) precedes v (0x76) — reintroducing exactly the
budget-exhaustion the ordering exists to prevent. Now sorted on the same
uppercase normalisation the filters apply.

Refusing a name that round-trips to empty aborted the WHOLE plan. A sidecar
folder named with a single emoji made a backup un-rippable that 1.6.0 handled
fine, and reported it as a collision with a file that does not exist. It is now
skipped with a warning: the entry is unaddressable either way, but one
irrelevant file should not cost the user their rip.

The mtime check now applies only to files whose CONTENT the plan read — the
IFOs, whose bytes 0xC0/0xC4 place every VOB. Everything else is planned from
size alone, which is already checked, so comparing mtime there bought nothing
and risked a real false positive: disc backups commonly live on exFAT/FAT32,
which stores local time, so a long rip spanning a DST transition would see a
whole-hour shift on an untouched multi-gigabyte VOB and abort hours in.

src/dirimage/layout.rs

@@ -233,11 +233,23 @@ fn walk(dir: &Path, disc_path: &str, depth: u32, entries: &mut usize) -> Result<
         // exit 0. Comparing the raw host names cannot see that; deriving the
         // key from the same two functions cannot drift from it.
         let as_read = crate::udf::parse_udf_name(&crate::dirimage::encode::encode_cs0(&name));
-        // Nothing left after the reader is done with it: the entry would exist
-        // in the image and be unaddressable by any name. Refuse rather than
-        // write something no consumer can reach.
+        // Nothing left after the reader is done with it — a name made entirely
+        // of characters `parse_udf_name` drops, e.g. a sidecar folder named
+        // with a single emoji. The entry would exist in the image and be
+        // addressable by nothing.
+        //
+        // SKIP it, do not fail the plan. Failing turned an irrelevant extra
+        // file into an un-rippable folder that 1.6.0 handled fine (the
+        // unreachable entry merely sat there, harming nothing), and reported it
+        // as a collision with a file that does not exist. It is also not
+        // pushed to `names`, so it cannot collide with anything either.
         if as_read.is_empty() {
-            return Err(Error::DirNameCollision { host: child_path });
+            tracing::warn!(
+                target: "freemkv::dirimage",
+                path = %child_path,
+                "name is unrepresentable in UDF after encoding; entry omitted from the image"
+            );
+            continue;
         }
         names.push(as_read.to_ascii_uppercase());
         if ft.is_dir() {

src/dirimage/mod.rs

@@ -127,11 +127,28 @@ impl DirImage {
         let mut files = Vec::with_capacity(nodes.len());
         let mut ranges = Vec::new();
         for (idx, node) in nodes.iter().enumerate() {
+            // Carry the plan-time mtime ONLY for files whose CONTENT the plan
+            // read — the DVD IFOs, whose bytes 0xC0/0xC4 decide where every VOB
+            // is placed (`layout::place_video_ts` -> `read_head`).
+            //
+            // For every other file the plan depends on the SIZE alone, and size
+            // is already checked. Comparing mtime on those buys nothing and
+            // costs real false positives: disc backups commonly live on
+            // exFAT/FAT32, which stores local time, so a long rip spanning a
+            // DST transition sees a whole-hour shift on a file nobody touched
+            // and would abort hours in, blaming a change that did not happen.
+            // The multi-gigabyte VOBs are exactly the files a long rip re-opens
+            // after the handle cache evicts them.
+            let content_sensitive = node
+                .disc_path
+                .rsplit('.')
+                .next()
+                .is_some_and(|e| e.eq_ignore_ascii_case("IFO"));
             files.push(FileRef {
                 host: node.host.clone(),
                 disc_path: node.disc_path.clone(),
                 size: node.size,
-                mtime: node.mtime,
+                mtime: content_sensitive.then_some(node.mtime).flatten(),
             });
             let mut offset = 0u64;
             for e in &node.extents {

src/disc/extract.rs

@@ -318,7 +318,13 @@ impl Disc {
                 vts_group_of(&pf.disc_name).as_deref() == Some(vts) && is_title_vob(&pf.disc_name)
             })
             .collect();
-        files.sort_by(|a, b| a.disc_name.cmp(&b.disc_name));
+        // Case-INSENSITIVE, matching `vts_group_of`/`is_title_vob`, which
+        // selected these files case-insensitively. A byte-wise sort put
+        // 'V' (0x56) before 'v' (0x76), so a set holding `vts_01_1.vob`
+        // alongside `VTS_01_2.VOB` — reachable on a case-sensitive volume —
+        // started the crack at part 2 and could exhaust the budget in a clear
+        // run, which is the whole failure this ordering exists to prevent.
+        files.sort_by_key(|f| f.disc_name.to_ascii_uppercase());
 
         let mut extents: Vec<crate::disc::Extent> = Vec::new();
         for pf in files {