fix(path-resolve): try full relative path first in shared resolver

ROOT CAUSE of the quality scanner's "18/18 could not be probed". The shared
resolver (core/library/path_resolver.py) suffix-walked starting at index 1,
which is correct for absolute media-server paths (/music/Artist/... — index 0
is the empty leading segment) but WRONG for SoulSync's own library, which
stores RELATIVE paths like "Asketa/Another Side/track.flac". Index 0 there is
the artist folder; dropping it meant the resolver joined base/Another Side/...
(no artist) and nothing ever matched — so every library track came back
unresolved and the probe opened a relative path that didn't exist from CWD.

Start the suffix walk at index 0 so the FULL relative path is tried first.
Safe for absolute paths (i=0 yields base//Artist/... which harmlessly misses
and falls through to i=1) and Windows drive parts (E: fails on POSIX, falls
through). Other tools (orphan/fake-lossless detectors) were unaffected because
they os.walk the transfer folder directly and never used this resolver.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

core/library/path_resolver.py

@@ -224,10 +224,23 @@ def resolve_library_file_path_with_diagnostic(
     if not base_dirs:
         return None, attempt
 
-    # Skip index 0 to avoid drive-letter / leading-slash artifacts
-    # (e.g. "E:" or "" from a leading "/").
+    # Try progressively shorter path suffixes against each base dir.
+    #
+    # Start at index 0 so a clean RELATIVE library path is tried in FULL first.
+    # SoulSync's own library scanner stores paths like
+    # "Asketa/Another Side/01 - Track.flac" (no leading slash) — index 0 is the
+    # artist folder and dropping it (the old range(1, ...)) meant the artist
+    # segment was never joined, so nothing under transfer/ ever resolved and
+    # every track looked unreadable to the quality scanner.
+    #
+    # For ABSOLUTE media-server paths ("/music/Artist/Album/track.flac") index 0
+    # is the empty leading segment and i=0 yields os.path.join(base, "", ...) ==
+    # base/Artist/... which simply won't exist and harmlessly falls through to
+    # i=1 ("music/...") etc. A Windows drive part ("E:") at i=0 likewise just
+    # fails on POSIX and falls through. So starting at 0 is safe for every form
+    # and only ADDS the relative-full-path match that was missing.
     for base in base_dirs:
-        for i in range(1, len(path_parts)):
+        for i in range(0, len(path_parts)):
             candidate = os.path.join(base, *path_parts[i:])
             if os.path.exists(candidate):
                 return candidate, attempt

tests/library/test_path_resolver.py

@@ -74,6 +74,25 @@ def test_finds_file_via_transfer_folder_suffix_walk(tmp_path: Path) -> None:
     assert result == str(actual)
 
 
+def test_finds_file_via_relative_db_path_full_suffix(tmp_path: Path) -> None:
+    """SoulSync's own library scanner stores RELATIVE paths with NO leading
+    slash, e.g. "Artist/Album/track.flac". Index 0 is the artist folder, so the
+    resolver must try the FULL path first — the old range(1, ...) dropped the
+    artist segment and every such track came back unresolved (quality scanner:
+    "could not be probed"). Regression guard for that fix."""
+    transfer = tmp_path / "Transfer"
+    (transfer / "Asketa" / "Another Side").mkdir(parents=True)
+    actual = transfer / "Asketa" / "Another Side" / "01 - Another Side.flac"
+    actual.write_bytes(b"audio")
+
+    result = resolve_library_file_path(
+        "Asketa/Another Side/01 - Another Side.flac",
+        transfer_folder=str(transfer),
+    )
+
+    assert result == str(actual)
+
+
 def test_finds_file_via_download_folder_when_transfer_misses(tmp_path: Path) -> None:
     transfer = tmp_path / "Transfer"
     transfer.mkdir()