Phase 1c.2.1 splits each wishlist invocation into per-album sub-
batches so the album-bundle dispatch can engage once per album.
Side effect: the completion handler ``finalize_auto_wishlist_completion``
ran end-of-run logic (cycle toggle + state reset + automation
event emit) once per BATCH, so a 2-album run fired the cycle
toggle twice + emitted two ``wishlist_processing_completed``
events. The cycle landed at the right value either way but the
state machine had become per-batch instead of per-run.
Fix: reify "wishlist run" as a first-class concept via a shared
``wishlist_run_id`` UUID. Generated once per wishlist invocation
in both the auto- and manual-wishlist paths, stamped on every
sub-batch row in ``download_batches``.
``finalize_auto_wishlist_completion`` now reads the completing
batch's ``wishlist_run_id`` and, when present, scans
``download_batches`` for siblings still in pre-terminal phases.
If any sibling is still active, the per-batch summary records
but the cycle toggle + state reset + automation emit are
deferred. Only the last completing sibling fires the run-level
finalization. Legacy single-batch runs (no run_id field) keep
their toggle-immediately behavior — back-compat by absence.
The run_id also lays groundwork for frontend grouping (one
logical row in the Downloads view per wishlist run instead of N
sibling rows), but that UX work is deferred.
3 new tests in ``test_processing.py`` pin: defer-when-siblings-
active, toggle-when-last-sibling-done, back-compat-without-run_id.
1 new assertion in ``test_automation.py`` confirms all sub-batches
of one auto-wishlist invocation share the same run_id. 309 tests
across wishlist + automation suites green.
Notes: dispatch concurrency unchanged — sub-batches still run via
the shared download worker pool. Slskd serializes per-uploader at
its own layer (same uploader = automatic queue, different
uploaders = legit parallel), so SoulSync-side serial enforcement
would duplicate work the right layer already handles.