The auto and manual wishlist flows each built the same ~20-field
download_batches row in separate places (auto album, auto residual, manual
placeholder, manual sub-batches) — four near-identical literals that could (and
did) drift apart, producing subtly different batch shapes between the flows.
Extract make_wishlist_batch_row() as the single source of truth: it emits the
consistent core field set, with the genuinely per-flow differences as explicit
arguments — initial phase ('queued' for auto / 'analysis' for manual), the
auto-only auto_initiated/auto_processing_timestamp/current_cycle via
extra_fields, and album-vs-residual contexts. All four sites now go through it,
so every wishlist batch has an IDENTICAL shape (this also removes the field
drift that confused the modal-hydration code).
Deliberately NOT unified — and left explicit in each caller, per the
'don't cargo-cult genuinely-different code' principle: the grouping decision
(auto groups only on the albums cycle), batch-id allocation (manual reuses the
caller's placeholder id for the first sub-batch), and dispatch (auto
parallel-submits album batches to the dedicated pool + residual to the shared
pool; manual runs them serially on one thread). Those are real behavioral
differences, not duplication.
Behavior-preserving: verified safe to normalize the row shape (grep confirmed
every reader uses .get() with defaults, no key-presence checks). The existing
auto (test_automation.py) and manual (test_manual_download.py) characterization
suites stay green = differential proof of identical behavior. Adds
test_batch_factory.py (core fields, album/residual, extra_fields, no shared
mutable state, consistent key shape). 131 wishlist tests pass.
