fix(video): fix two remaining bugs in Specials numbering and long-season episodes

1. A season spanning more than one folder (a per-book Bonus folder nested
   inside every numbered season) got the same synthetic episode numbers
   handed out again in each folder independently — three unrelated
   Specials all showing up as "S0E01". _synthetic_episode_number now ranks
   across the whole show for the target season, not just one file's own
   folder.

2. guessit reads a bare 3-digit leading episode number as a concatenated
   season+episode guess rather than a plain episode number — "100" parses
   as season=1, episode=0, not episode=100, with nothing in its output
   distinguishing that from a real 2-digit episode. A season-like ancestor
   already overrides guessit's season (previous commit); this applies the
   same fix to episode via a direct regex on the leading number, capped at
   3 digits so a leading year (4 digits) is never misread the same way.

Both confirmed against the real library this whole fix was found on:
per-book Bonus features across two books no longer collide, and a real
100th-episode file now resolves to episode 100 instead of 0.

2 files changed, 73 insertions, 22 deletions

diff --git a/packages/meshbay-node/src/meshbay_node/indexer/enrich.py b/packages/meshbay-node/src/meshbay_node/indexer/enrich.py
index 5535674..07f0be7 100644
--- a/packages/meshbay-node/src/meshbay_node/indexer/enrich.py
+++ b/packages/meshbay-node/src/meshbay_node/indexer/enrich.py
@@ -36,9 +36,14 @@ MAX_ANCESTOR_DEPTH = 4
 # Bounds the "borrow a title from a sibling episode filename" scan (§3.4) so
 # a folder with thousands of files costs a fixed, small amount of work.
 MAX_SIBLINGS_CHECKED = 20
+# Bounds the whole-show scan _synthetic_episode_number uses to rank a
+# season's files across more than one folder (§3.4c) — a show's total file
+# count, not just one folder's, so this needs more headroom than
+# MAX_SIBLINGS_CHECKED.
+MAX_SEASON_FILES_CHECKED = 500
 
 
-def _season_and_show_from_ancestors(file_path: Path) -> tuple[int, str] | None:
+def _season_and_show_from_ancestors(file_path: Path) -> tuple[int, Path] | None:
     """
     §3.4/§3.4c: walk up ancestor folders for a season-like one (a numbered
     season, or Specials/Bonus/Extras -> season 0) — season from the first
@@ -72,7 +77,7 @@ def _season_and_show_from_ancestors(file_path: Path) -> tuple[int, str] | None:
                 folder = folder.parent
                 depth += 1
                 continue
-            return season, folder.name
+            return season, folder
         if season is None:
             season = this_season
         folder = folder.parent
@@ -112,27 +117,45 @@ def _title_from_siblings(file_path: Path) -> str | None:
     return None
 
 
-def _synthetic_episode_number(file_path: Path) -> int:
+def _synthetic_episode_number(file_path: Path, show_root: Path, season: int) -> int:
     """
-    §3.4b: a Specials/Bonus folder's files often carry no episode number at
-    all — each is just named after its own one-off title. The frontend
-    (video-app.js's buildSeasons) sorts within a season by this number but
-    only needs it to provide a stable order, not to mean anything beyond
-    that — alphabetical rank among the folder's video files is enough, and
-    deterministic across re-scans as long as the folder's contents don't
-    change. 1-based so it reads as "episode 1", not "episode 0", in a UI
-    that already uses season 0 for "Specials" itself.
+    §3.4b/§3.4c: a Specials/Bonus folder's files often carry no episode
+    number at all — each is just named after its own one-off title. The
+    frontend (video-app.js's buildSeasons) sorts within a season by this
+    number but only needs it to provide a stable order, not to mean
+    anything beyond that.
+
+    Ranked across the *whole show*, not just this file's own folder: season
+    0 routinely spans more than one folder under the show's root — a
+    Bonus folder nested inside every numbered season
+    (`Show/Season N/Bonus/...`) is exactly the shape that produces this —
+    and ranking within just this file's own folder hands out the same
+    "episode 1" again in every other one, found live as three unrelated
+    Specials all showing up as "S0E01". Deterministic across re-scans as
+    long as the show's contents don't change. 1-based so it reads as
+    "episode 1", not "episode 0", in a UI that already uses season 0 for
+    "Specials" itself. Bounded (MAX_SEASON_FILES_CHECKED) so a huge show
+    costs a fixed amount of work rather than scaling with its size.
     """
     try:
-        names = sorted(
-            p.name for p in file_path.parent.iterdir()
-            if p.is_file() and p.suffix.lower() in MEDIA_EXTENSIONS["video"])
+        candidates = sorted(
+            (p for p in show_root.rglob("*")
+             if p.is_file() and p.suffix.lower() in MEDIA_EXTENSIONS["video"]),
+            key=lambda p: (str(p.parent), p.name),
+        )
     except OSError:
         return 1
-    try:
-        return names.index(file_path.name) + 1
-    except ValueError:
-        return 1
+    rank = 0
+    for i, candidate in enumerate(candidates):
+        if i >= MAX_SEASON_FILES_CHECKED:
+            break
+        ancestor = _season_and_show_from_ancestors(candidate)
+        if ancestor is None or ancestor[0] != season:
+            continue
+        rank += 1
+        if candidate == file_path:
+            return rank
+    return 1
 
 
 async def _make_thumbnail(file_path: Path, duration: float | None) -> bytes | None:
@@ -242,11 +265,22 @@ class Enricher:
                 # individual "movies" each searched against — and matched
                 # to — an unrelated real film sharing that one-off title,
                 # instead of anything grouped under the show at all.
-                season, show_title = ancestor
-                episode = ep.episode
+                season, show_folder = ancestor
+                # Not ep.episode: guessit reads a bare 3-digit leading
+                # number (routine once a season-like ancestor is already
+                # doing the real season/episode work) as a concatenated
+                # season+episode guess rather than a plain episode number
+                # — confirmed live, "100    Title.mkv" parsed as episode 0,
+                # not 100, with nothing in guessit's own output telling
+                # that apart from a real 2-digit episode. The direct regex
+                # reads the whole leading number as it is.
+                episode = title_parse.leading_episode_number(entry.name)
+                if episode is None:
+                    episode = ep.episode
                 if episode is None:
-                    episode = await asyncio.to_thread(_synthetic_episode_number, file_path)
-                fields["display_title"] = show_title
+                    episode = await asyncio.to_thread(
+                        _synthetic_episode_number, file_path, show_folder, season)
+                fields["display_title"] = show_folder.name
                 fields["season"] = season
                 fields["episode"] = episode
             elif ep.episode is not None:
diff --git a/packages/meshbay-node/src/meshbay_node/indexer/title_parse.py b/packages/meshbay-node/src/meshbay_node/indexer/title_parse.py
index 0baf34f..985bd7a 100644
--- a/packages/meshbay-node/src/meshbay_node/indexer/title_parse.py
+++ b/packages/meshbay-node/src/meshbay_node/indexer/title_parse.py
@@ -229,3 +229,20 @@ def parse_episode_filename(filename: str) -> ParsedName:
         display_title=title or None, naive_title=nt,
         season=season, episode=episode, confidence=confidence,
     )
+
+
+# A bare leading episode number, no show name attached (§3.4c) — the same
+# shape as music's _TRACK_PREFIX_RE, capped at 3 digits for the same reason:
+# a leading year ("2010 - Episode.mkv") is 4 digits and must not match.
+# guessit's own `episode` is not a substitute here: given exactly 3 digits it
+# tries to read them as a concatenated SxxE/SEE season+episode pair instead
+# of a plain episode number — confirmed live, "100    Title.mkv" parses as
+# season=1, episode=0, not episode=100 — silently wrong in a way nothing
+# about its output distinguishes from a real 2-digit episode. This reads the
+# whole leading number as one value instead.
+_LEADING_NUMBER_RE = re.compile(r"^(\d{1,3})[\s._-]+(?=\S)")
+
+
+def leading_episode_number(filename: str) -> int | None:
+    m = _LEADING_NUMBER_RE.match(filename)
+    return int(m.group(1)) if m else None