Pulls the 201-line staging-folder shortcut out of `web_server.py` into
its own module under the existing `core/downloads/` package. Pure 1:1
lift — wrapper keeps the original entry-point name so the task worker's
existing call site continues to work without changes.
What `try_staging_match` does:
1. Pull the per-batch staging-file cache (one filesystem scan per batch).
2. For each staging entry, compute title + artist similarity using
SequenceMatcher and the matching engine's `normalize_string`. Require
title >= 0.80, then a combined score >= 0.75. The weighting flips
based on whether artist info is available on both sides:
- both have artist: 0.55*title + 0.45*artist
- either side missing artist: 0.80*title + 0.20*artist (lean on title)
3. Copy the matched file to the configured transfer dir (with a
"_staging" suffix when the destination filename already exists, to
avoid overwriting a legitimate prior download).
4. Mark the task as 'post_processing', username='staging',
staging_match=True.
5. Build a synthetic spotify_artist / spotify_album context (mirroring
the modal-worker logic so the file-organization template applies
cleanly) and store it under "staging_<task_id>". Two paths:
- Explicit context branch (track_info has _is_explicit_album_download)
→ real album/artist data copied through.
- Fallback branch → synthesized from track + track_info, with
`is_album_download` heuristically derived (album differs from title
and isn't "Unknown Album").
6. Hand off to `_post_process_matched_download_with_verification` which
does tagging, path building, AcoustID verification, and DB insertion.
Returns True if the staging shortcut won; False to fall through to the
normal Soulseek search path.
Dependencies injected via `StagingDeps` (5 fields) — config_manager,
matching_engine, get_staging_file_cache, docker_resolve_path,
post_process_matched_download_with_verification.
Diff vs original after `deps.X` → global X normalization is **zero
differences** — 201 lines orig = 201 lines lifted, byte-identical body
(including all whitespace, comments, log strings, and the inline
`from difflib import SequenceMatcher` / `import shutil` imports inside
the function body).
Tests: 9 new under tests/downloads/test_downloads_staging.py covering
no staging files / no track title / low-confidence match returning
False, exact match copying file + transitioning task state + invoking
post-processing, existing-file rename via `_staging` suffix, explicit
album context branch, fallback context synthesis (with both album-as-
album and album-equals-title cases), and copy failure (missing source
file) returning False.
Full suite: 1308 passing (was 1299). Ruff clean.
a2e068eaba