# Terminal assignment status loses the durable scan deadline

Status: open and reproducible on the live `sec` validation cohort.

## Impact

`GET /api/v1/worker/assignments/{reservation_id}` can return
`deadlines.scan_deadline_at: null` for a resolved assignment even though the
durable terminal receipt contains the concrete scan deadline. The same response
labels the deadline set as immutable, so replay no longer faithfully exposes the
receipt that was committed at bundle acceptance.

Receipt, payload, scan-event, diagnostic, and reservation identities remain
correct. The loss is limited to terminal status readback of the scan deadline.

## Live evidence

The accepted Linux assignment used for this check had:

- a durable `bundle_accepted` receipt with a concrete `scan_deadline_at`;
- a later persisted `awaiting_receipt` progress event with
  `scan_deadline_at: null`;
- a successful authenticated status response whose terminal receipt fields all
  matched PostgreSQL, except that `scan_deadline_at` had become null.

The complete API response is retained locally as
`D:\truf\worker-linux-terminal-status-raw.json` with SHA-256
`0954e40b4ccb6921bbd572abb3d4898ee56e2955345de21ed7df5f85177536d1`.
The durable receipt is retained in
`build/live-trace-20260925/raw-evidence-expanded.json`.

## Root cause

`ScannerDB.remote_assignment_status()` loads the durable receipt and then calls
`result.update(observability)` (`app/scanner_db.py` around lines 16707-16710).
The observability object reconstructs its complete `deadlines` object from the
latest progress row. Its `scan_deadline_at` comes only from
`event.get('scan_deadline_at')` (`app/scanner_db.py` around lines 16588-16605).

Consequently, a later progress event with a null scan deadline replaces the
entire deadline object stored in the terminal receipt. This is a readback merge
problem; the persisted receipt itself is unchanged and correct.

## Expected correction

For resolved assignments, preserve the durable receipt's immutable deadline
object while overlaying only live observability fields such as latest progress,
known reason, and diagnostic authority. Add PostgreSQL regression coverage where
the accepted receipt has a concrete scan deadline and a later progress event has
a null deadline.