Cutscene voice: resolve movies via continuous-stream cue regions

Cracked how the game maps a movie to its voice track and reimplemented it,
fixing wrong/short voices for RT and hokyu cutscenes.

## Mechanism (RE'd from a Canary file-I/O trace, user-confirmed by ear)

The movie voices are ONE continuous XMA stream, physically chunked into
`<lang>\Movie\VOICE_*.slb` (and `\etc\VOICE_D_*.slb`) sound.pak TOC entries
whose boundaries do NOT align with the cutscene cues. A single cue routinely
spans two `.slb` chunks, so a `.slb` does not necessarily hold the track its
name claims (they are off-by-one vs the cues). Each cue ends at an inline
trailer descriptor `(sound_id:u32be, 0x11, …)` whose id repeats at +0x800.

Resolution chain (all derivable on-disc, no guest-code RE):
  1. movie -> cue token         (ADVERTISE_MOVIE manifest VOICETRACK)
  2. cue token -> sound-id       (master sound registry, tables.pak
                                  a2c8c185=eng / b04238e0=jpn, schema 0x13cb84ba)
  3. sound-id -> [start,end)      scan the stream for trailer(id) and its
                                  predecessor; cue audio = the bytes between,
                                  read continuously across chunk boundaries.

Validated: decoded voice length matches each movie within ~0.4s, including
cross-boundary cues (ADV/RT01A/RT01B/RT01C/S00A/S01A + the 5 bound hokyu).

## Changes

- sylpheed-formats/src/movie_voice.rs (new): registry_voice_ids(),
  find_descriptor(), find_descriptor_before() (gap-tolerant predecessor).
  Unit-tested.
- viewer iso_loader.rs: resolve_movie_voice_region() + decode_voice_region()
  (continuous read via existing read_segment_range + to_xma_riffs). Voice/
  audio requests now region-first; a `\Movie\` token that fails region stays
  SILENT (never plays the wrong off-by-one chunk). Removed the old
  movie_is_demo_based suppress hack.
- Anchor tries subdirs Movie/etc/Voice so hokyu `\etc\VOICE_D_*` resolve too.
- Examples resolve_all/validate_cues/hokyu_final document + validate the pipeline.

## Status

- RT / S / ADV cutscene voices: CORRECT (user-confirmed).
- 5 manifest-bound hokyu (VOICE_D_450-454): CORRECT (user-confirmed).

## OPEN (handoff)

13 of 18 hokyu movies have NO manifest VOICETRACK; the game reuses the 5
recordings across stages via a code rule. `hokyu_fallback_token()` currently
guesses by category (ship LS/DS x source carrier-A/tanker-H: LS/A->450,
LS/H->453, DS/A->452, DS/H->454). USER REPORTS THIS IS SOMETIMES WRONG.
- LS/carrier has two takes (450 from s02A, 451 from s09A); the early-vs-late
  split is unknown — unbound LS/A currently all default to 450.
- Definitive fix = Canary `--phase_a_fileio_only` file.read trace of an unbound
  hokyu (e.g. hokyu_LS_s03A) to see which VOICE_D the game actually streams,
  then encode the real rule. Same method that cracked the RT mapping.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

crates/sylpheed-formats/src/movie_subtitle.rs

@@ -162,6 +162,43 @@ pub fn track_demo_ids(lang_pak: &PakArchive, movie_basename: &str) -> Vec<u32> {
         .collect()
 }
 
+/// Per-line `(demo id, start seconds)` for a movie's timing track — the radio-box
+/// voice schedule. Each `MSG_DEMO_<id>` reference takes the start time of the
+/// timing that follows it (a caption may list two demo lines under one timing;
+/// both then share that start). Empty for inline-text / absent tracks (those are
+/// story movies whose voice is the single manifest `VOICETRACK`, not per-line).
+pub fn track_voice_cues(lang_pak: &PakArchive, movie_basename: &str) -> Vec<(u32, f32)> {
+    let Some(Ok(track)) = lang_pak.read_by_hash(track_key(movie_basename)) else {
+        return Vec::new();
+    };
+    if !is_ixud(&track) {
+        return Vec::new();
+    }
+    let toks = utf16le_tokens(&track);
+    let start = toks
+        .iter()
+        .position(|t| t.ends_with("SUBTITLE"))
+        .map(|i| i + 1)
+        .unwrap_or(0);
+    let mut out = Vec::new();
+    let mut pending: Vec<u32> = Vec::new();
+    for tok in &toks[start..] {
+        match parse_timing(tok) {
+            Some((s, _)) => {
+                for d in pending.drain(..) {
+                    out.push((d, s));
+                }
+            }
+            None => {
+                if let Some(d) = demo_ref(tok) {
+                    pending.push(d);
+                }
+            }
+        }
+    }
+    out
+}
+
 /// Build `demo id → ordered caption lines` from a `GP_MAIN_GAME_<L>` pack.
 ///
 /// Scans every IXUD block, pairing each text token with the immediately