Sokhi: some tracks in a multi-disc album showed up with a null disc in Jellyfin
and floated ungrouped above the disc sections (tracks 3/9/15). Mechanism: the tag
writer only wrote the disc tag when disc_number was truthy, and enrichment CLEARS
all tags before rewriting — so a track whose disc came back 0 / None / '' lost its
disc entirely. Those falsy values slipped through because source.py defaulted with
'is not None' (a literal 0 passed) and context.py's or-chain can yield None; this
happens especially when a track resolves to a different edition than its siblings.
Fix: normalize_disc_number() floors any value to >=1, and enrichment now writes the
disc tag UNCONDITIONALLY (like the track number) so a track is never disc-less.
source.py uses the same floor so the metadata dict (and the 'Disc N' folder org)
stays consistent. Valid multi-disc values are preserved untouched.
Tests: normalize floors 0/None/''/negatives/non-numeric -> 1, preserves 1..4 and
tolerates '2.0'. 1406 enrich/metadata/track-number tests green, ruff clean.
NOTE: this fixes the SYMPTOM (never ungrouped). The deeper cause — a track matching
a DIFFERENT edition/release than its album siblings (the Persona-box-set mismatch in
the sample file; the canonical-version problem) — is separate and still open.
c11a742e58