feat(library): delete archived prompts from the archived shelf (#492)

The archived shelf's bar offers Delete… after Restore. Its review is the
permanent delete only (no Archive choice: the prompts are archived
already), with #482's grid, safety backup, review digests, records hold
and epoch fence. A prompt used as another prompt's negative stays
archived; one restored since the shelf was read is kept and counted.

The preview and delete routes take an optional shelf ('active' or
'archived'). The held write classifies the same shelf, so the permanent
delete is backed up; on this shelf the write archives and rewrites
nothing and counts every reviewed id it did not delete as changed.

database/library_archive.py

@@ -49,7 +49,26 @@ _NEGATIVE_OF_OTHER = (
     "WHERE op.negative_prompt_id=p.id AND op.positive_prompt_id!=p.id)"
 )
 # Classes in the order a prompt is tested; the first that holds wins.
-CLASSES = ("not_found", "protected", "already_archived", "archive", "delete")
+CLASSES = (
+    "not_found",
+    "protected",
+    "already_archived",
+    "not_archived",
+    "archive",
+    "delete",
+)
+# #492: the shelf a Delete… runs on. On the archived shelf an archived prompt is
+# classified by its pairs, and one restored since is ``not_archived``.
+SHELVES = ("active", "archived")
+
+
+def _check_shelf(shelf: str) -> bool:
+    """Whether ``shelf`` is the archived shelf (ValueError when unknown)."""
+    if shelf not in SHELVES:
+        raise ValueError("shelf must be active or archived")
+    return shelf == "archived"
+
+
 _DIGEST = re.compile(r"^[0-9a-f]{64}$")
 
 
@@ -86,8 +105,9 @@ class LibraryArchiveOperations:
     """PromptDatabase mixin: classify, archive or delete, and restore parents."""
 
     def _classify_library_delete(
-        self, conn: sqlite3.Connection, prompt_ids: list[int]
+        self, conn: sqlite3.Connection, prompt_ids: list[int], shelf: str = "active"
     ) -> dict:
+        on_archived_shelf = _check_shelf(shelf)
         found, deletable = {}, set()
         for chunk in _batches(prompt_ids):
             marks = ",".join("?" for _ in chunk)
@@ -100,7 +120,9 @@ class LibraryArchiveOperations:
                 protected, archived, paired, negative_of_other = row[1:5]
                 if protected:
                     found[row[0]] = "protected"
-                elif archived:
+                elif on_archived_shelf and not archived:
+                    found[row[0]] = "not_archived"
+                elif archived and not on_archived_shelf:
                     found[row[0]] = "already_archived"
                 elif paired:
                     found[row[0]] = "archive"
@@ -237,18 +259,20 @@ class LibraryArchiveOperations:
         return list(dict.fromkeys(prompt_ids))
 
     def classify_library_delete(
-        self, prompt_ids: list[int], *, expected_epoch: str
+        self, prompt_ids: list[int], *, expected_epoch: str, shelf: str = "active"
     ) -> dict:
         """What a delete of ``prompt_ids`` would do now (reads only).
 
         Returns the id lists per class, in request order, ``image_links``
         (the image link rows the ``delete`` class would remove) and
-        ``fingerprints`` of the ``delete`` class (``_fingerprints``).
+        ``fingerprints`` of the ``delete`` class (``_fingerprints``). On the
+        archived ``shelf`` (#492) archived prompts are classified by their pairs.
         """
+        _check_shelf(shelf)
         prompt_ids = self._checked_ids(prompt_ids, expected_epoch)
         with self.library_snapshot() as (conn, _epoch, _ceiling):
             epoch = self._library_epoch(conn, expected_epoch)
-            classes = self._classify_library_delete(conn, prompt_ids)
+            classes = self._classify_library_delete(conn, prompt_ids, shelf)
             deletable = classes["deletable"]
             return {
                 "library_epoch": epoch,
@@ -290,6 +314,7 @@ class LibraryArchiveOperations:
         expected_epoch: str,
         candidates: dict | None,
         delete_paired: dict | None = None,
+        shelf: str = "active",
     ) -> dict:
         """Archive and delete what the user reviewed, all or nothing.
 
@@ -305,7 +330,12 @@ class LibraryArchiveOperations:
         Delete permanently to their review digest. Each is deleted with its
         own saved pairs only while it is still deletable and its digest is
         unchanged; otherwise it is archived and counted ``changed``.
+
+        On the archived ``shelf`` (#492) the ids are archived already: nothing
+        is archived or rewritten, every reviewed id not deleted (protected or
+        changed) counts ``changed``, and one restored since ``not_archived``.
         """
+        on_archived_shelf = _check_shelf(shelf)
         _validate_epoch(expected_epoch)
         for ids in (archive_ids, delete_ids):
             if not isinstance(ids, list) or any(
@@ -330,7 +360,7 @@ class LibraryArchiveOperations:
         prompt_ids = list(dict.fromkeys([*archive_ids, *delete_ids]))
         with self._pair_transaction() as conn:
             epoch = self._library_epoch(conn, expected_epoch)
-            classes = self._classify_library_delete(conn, prompt_ids)
+            classes = self._classify_library_delete(conn, prompt_ids, shelf)
             now_prints = self._fingerprints(conn, classes["delete"])
             deletes, archives, changed = [], [], 0
             paired_now = set(classes["deletable"])
@@ -356,6 +386,11 @@ class LibraryArchiveOperations:
                 else:
                     changed += 1
             changed += len(classes["protected"])
+            if on_archived_shelf:
+                # Already archived: the rest stay as they are, each one counted.
+                archives = []
+                changed = len(prompt_ids) - len(deletes) - len(paired_deletes)
+                changed -= len(classes["not_found"]) + len(classes["not_archived"])
             image_links = self._image_links(conn, [*deletes, *paired_deletes])
             now = utc_now_iso()
             for pid in archives:
@@ -393,6 +428,7 @@ class LibraryArchiveOperations:
                 "deleted": deleted,
                 "archived": len(archives),
                 "already_archived": len(classes["already_archived"]),
+                "not_archived": len(classes["not_archived"]),
                 "not_found": len(classes["not_found"]),
                 "changed": changed,
                 "image_links": image_links,