Reported: Clear History button on the Import page left zombie rows
behind. Every survivor showed "⧗ Processing" status from 2-9 days ago.
Trace: `_record_in_progress` inserts a `status='processing'` row up-front
so the UI can render the in-flight import while it runs; `_finalize_result`
updates it to `completed`/`failed` when the import finishes. When the
worker is killed mid-import (server restart, crash), the row never gets
finalized — stays at `processing` forever. The clear-history endpoint's
SQL `DELETE ... WHERE status IN (...)` listed every terminal status but
omitted `processing`, so zombies survived every click.
Fix: add `processing` to the delete list, but guard against nuking
genuinely-live imports by intersecting against the worker's
`_snapshot_active()` map — any folder hash currently registered in
`_active_imports` is excluded from the delete via an `AND folder_hash
NOT IN (...)` clause. `pending_review` deliberately left out so user
still has to approve/reject those explicitly.
One endpoint touched (`/api/auto-import/clear-completed` in
web_server.py). No worker changes — guard reuses the existing
`_snapshot_active()` method that the UI poller already calls.
5 new tests in `tests/imports/test_auto_import_clear_completed_endpoint.py`:
- Zombie `processing` rows swept, live `processing` row preserved
(folder_hash currently in `_active_imports` survives)
- Response count matches actual delete count
- Empty active-set branch (unparameterized DELETE) — pinned because
an empty SQL `IN ()` would be a syntax error
- Worker-unavailable returns 500 (pre-existing guard not regressed)
- `pending_review` rows always survive — never auto-swept
Full pytest sweep: 2758 passed (one pre-existing flaky timing test
on `test_import_singles_parallel.py` failed under full-suite CPU load,
passes in isolation in 2.95s — unrelated to this change).
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