fix(review): never queue an ambiguous file with nothing to choose

The maintainer's live queue held 39 items whose candidates all read
"unresolved" ("No positive / No negative"). An ambiguous result is now
reviewable only when at least two candidates are resolved with non-blank
positive text. With none the file could not be traced; with exactly one,
the untraced branches may still have made the file, so that text is not
certain either. Both are reported unresolved, never linked and never
queued (also the A1111 two-delimiter case, which has no candidates).

A rescan removes the pending items of such files whose own evidence
offers no choice, with the same safe delete as the linked settle
(pending, revision 0, no decision row). A limited item (over 16 candidates) that holds at least two
candidates is kept. The job scope gains review_untraced and the log
"= N images left Needs review · nothing to choose".

database/review.py

@@ -39,6 +39,7 @@ from .review_schema import (
     METADATA_TABLE,
     canonical_evidence,
     evidence_digest,
+    evidence_offers_choice,
 )
 
 # Only this module's table constants are interpolated into the SQL below.
@@ -95,6 +96,13 @@ _PENDING_OF_LOCATOR = (
     f"JOIN {ITEMS_TABLE} i ON i.byte_id=b.id "
     "WHERE f.locator=? AND i.state='pending'"
 )
+# Pending items of one file with their evidence: an untraced file's settle.
+_PENDING_EVIDENCE_OF_LOCATOR = (
+    f"SELECT i.id,i.evidence FROM {FILES_TABLE} f "  # nosec B608
+    f"JOIN {BYTES_TABLE} b ON b.file_id=f.id "
+    f"JOIN {ITEMS_TABLE} i ON i.byte_id=b.id "
+    "WHERE f.locator=? AND i.state='pending'"
+)
 # Only an undecided item goes: a decision row (RESTRICT) is never deleted.
 _SETTLE_ITEM = (
     f"DELETE FROM {ITEMS_TABLE} WHERE id=? AND state='pending' "  # nosec B608
@@ -417,6 +425,41 @@ class ReviewOperations:
                 conn.execute(_BUMP_REVIEW_INDEX)
         return removed
 
+    def settle_untraced_review_items(self, locators) -> int:
+        """Remove the pending, undecided items that offer nothing to choose.
+
+        ``locators`` are files the caller found ambiguous without a choice
+        (fewer than two candidates carry a prompt). Of their items, one leaves
+        the queue only when its own stored evidence offers no choice either
+        (``evidence_offers_choice``) and it is still ``pending`` at revision 0
+        with no decision row, the same safe delete as
+        ``settle_linked_review_items``. Files without a pending item cost one
+        indexed read and open no write transaction. Returns how many items
+        were removed (the review index revision moves when any was).
+        """
+        locators = list(locators)
+        for locator in locators:
+            _validate_locator(locator)
+        conn = self.model.get_connection()
+        pending = [
+            locator
+            for locator in locators
+            if conn.execute(_PENDING_OF_LOCATOR, (locator,)).fetchone() is not None
+        ]
+        if not pending:
+            return 0
+        removed = 0
+        with self._pair_transaction() as conn:
+            for locator in pending:
+                rows = conn.execute(_PENDING_EVIDENCE_OF_LOCATOR, (locator,)).fetchall()
+                for item_id, evidence in rows:
+                    if evidence_offers_choice(json.loads(evidence)):
+                        continue
+                    removed += conn.execute(_SETTLE_ITEM, (item_id,)).rowcount
+            if removed:
+                conn.execute(_BUMP_REVIEW_INDEX)
+        return removed
+
     def review_queue_page(self, *, limit: int, after: tuple | None = None) -> dict:
         """One page of pending items, oldest first, from one snapshot.
 

database/review_schema.py

@@ -200,6 +200,44 @@ def canonical_evidence(value: Any) -> str:
     return text
 
 
+def choosable(candidate: Any) -> bool:
+    """True when a candidate offers a prompt to choose: it is ``resolved`` and
+    its positive side carries non-blank text. The page disables any other
+    candidate, so it is never something to choose.
+    """
+    if not isinstance(candidate, dict) or candidate.get("state") != "resolved":
+        return False
+    positive = candidate.get("positive")
+    if not isinstance(positive, dict):
+        return False
+    text = positive.get("text")
+    return isinstance(text, str) and bool(text.strip())
+
+
+# An item is worth a decision only when at least this many candidates offer
+# a prompt; with fewer there is nothing to choose between (maintainer test of
+# #284/#288: 39 items whose candidates were all "unresolved").
+MIN_CHOOSABLE = 2
+
+
+def evidence_offers_choice(evidence: Any) -> bool:
+    """False when stored evidence provably offers nothing to choose.
+
+    Unlimited evidence must list ``MIN_CHOOSABLE`` choosable candidates. A
+    limited item stores none, only ``candidate_total``; it may offer a choice
+    (more than ``MAX_CANDIDATES`` prompts) unless that total is too small.
+    """
+    if not isinstance(evidence, dict):
+        return False
+    if evidence.get("limited"):
+        total = evidence.get("candidate_total")
+        return type(total) is int and total >= MIN_CHOOSABLE
+    candidates = evidence.get("candidates")
+    if not isinstance(candidates, list):
+        return False
+    return sum(1 for c in candidates if choosable(c)) >= MIN_CHOOSABLE
+
+
 def evidence_digest(text: str) -> str:
     """SHA-256 of canonical evidence text (ASCII, hence UTF-8 identical)."""
     return hashlib.sha256(text.encode("utf-8")).hexdigest()