New smart template variable that emits "CD01" / "CD02" etc. in filenames
on multi-disc albums, and expands to empty string on single-disc albums
so mixed libraries don't end up with "CD01" on every single.
Template behaviour:
- total_discs > 1 -> "CD{disc:02d}" (zero-padded, CD prefix)
- total_discs <= 1 -> empty string
- Both $cdnum and ${cdnum} bracket form supported
- Empty value collapses cleanly via existing double-dash regex plus new
leading-dash cleanup pass
Wiring:
- _apply_path_template in web_server.py (download pipeline)
- _apply_path_template in core/repair_jobs/library_reorganize.py
(Reorganize repair job)
- total_discs added to every album-mode template context:
* download pipeline album branch (uses resolved total_discs even for
single-track downloads from search)
* per-album Reorganize preview + apply endpoints (pre-scan all track
tags once, take max disc_number)
* Library Reorganize repair job (already had album_total_discs map,
just added to context dict)
Leading-dash cleanup added to _get_file_path_from_template (web_server)
and _build_path_from_template (library_reorganize) so templates like
"$cdnum - $track - $title" don't leave "- 05 - Title" on single-disc
albums.
UI:
- Template hint in Settings -> File Organization documents $cdnum
- Template validation variable list includes $cdnum
- Reorganize modal variable reference shows $cdnum with example "CD01"
Verified:
- Multi-disc disc 1 -> "CD01 - 05 - Track"
- Multi-disc disc 2 -> "CD02 - 05 - Track"
- Single-disc -> "05 - Track" (no leading dash)
- Templates without $cdnum behave unchanged
- 276/276 tests pass
78fa83c8ac
