fix(romhacks): only link library files that exist on disk

handoff.json lists files captured at routing time, but the
extraction-cruft cleanup later removes files extracted out of a kept
archive. The Caddy file_server can only serve real files (not archive
interiors), so existence-filter the art + guide rel-paths against
library/<slug>/ before embedding/linking them — dropping phantom
entries that would 404.

stacks/romhacks/orchestrator/render_catalog_notes.py

@@ -39,6 +39,17 @@ def load_handoff(slug):
     return {}
 
 
+def on_disk(slug, rels):
+    """Keep only the rel paths that actually exist under library/<slug>/.
+
+    The handoff record lists files captured at routing time, but the
+    extraction-cruft cleanup later removes files extracted out of a kept
+    archive — so a guide can be in handoff.json yet gone from disk (and the
+    file_server can only serve real files, not archive interiors)."""
+    base = LIBRARY / slug
+    return [rel for rel in rels if (base / rel).exists()]
+
+
 def pick_guides(guides, artifact):
     """Filter the raw handoff guide list to linkable docs/spreadsheets/extras.
 
@@ -152,10 +163,11 @@ def render(r):
     # Box art — embed from the internal Caddy file-server. Fall back to art
     # filenames in the metadata folder if the handoff record is missing them.
     ho = load_handoff(r["slug"])
-    art = ho.get("art") or []
+    art = on_disk(r["slug"], ho.get("art") or [])
     if not art and (META / r["slug"]).exists():
-        art = sorted(p.name for p in (META / r["slug"]).glob("*")
+        cand = sorted(p.name for p in (META / r["slug"]).glob("*")
                       if p.suffix.lower() in (".png", ".jpg", ".jpeg", ".webp", ".gif"))
+        art = on_disk(r["slug"], cand)  # only those also present in the served library
     for a in art:
         fm.append(f"![|320]({file_url(r['slug'], a)})")
     if art:
@@ -171,7 +183,7 @@ def render(r):
     if links:
         fm += ["## Download", ""] + [f"- {l}" for l in links] + [""]
     # Guides / spreadsheets / extras — link each to the served file.
-    guides = pick_guides(ho.get("guides", []), r["artifact"])
+    guides = pick_guides(on_disk(r["slug"], ho.get("guides", [])), r["artifact"])
     if guides:
         fm += ["## Guides & extras", ""]
         for rel in guides[:MAX_GUIDES]: