feat(model-grounded-detection): 4.1 guard dominance, 4.2 the missing sink facts

4.1 is the arbiter for the class no crash oracle reaches. An access-control bug
is the ABSENCE of a guard: no flow to follow, no crash to reproduce. What the
model can establish is a consistency violation -- an obligated operation no
discharging guard governs, in a file where its siblings are governed by one.

"Governed" turned out not to be one relation, and asking pure CFG dominance of
the operation gets two of three shapes wrong. Measured against the real engine:

  identity constraint  the guard is INSIDE the operation's arguments
                       filter_by(owner_id = current_user.id)
  identity branch      abort(403).controlledBy == [note.owner_id != current_user.id]
                       -- the check runs AFTER the fetch, so it never dominates
                       the operation, but it controls whether the value escapes
  dominating guard     a discharger-naming call that dominates the operation

That is why the query uses controlledBy rather than dominatedBy for shape 2.

Two bugs found by running it, both the same class as the sanitizer bug in group
2 -- part of a fact flattened, the part carrying the signal dropped:

  * dominance_specs used only `calls` and `decorators`, omitting
    identity_sources (current_user, request.user) and constraint_params
    (owner_id, user_id) -- which is how an identity constraint is actually
    written. The arbiter reported "no guard" on handlers that plainly had one.
    request_sources and permissive_values stay excluded: they describe the
    vulnerable shape, and including them would let the arbiter read a bug as
    its own fix.
  * matching operations by code containment yielded four or five desugared rows
    per operation (the bare `tmp1.filter_by` receiver among them, carrying none
    of the guards the real call has), so a guarded operation could be flagged.
    Matching is by call name now.

Live, deterministic, zero model calls:
  leaky      -> model_entailed  no discharging guard, while 2 sibling handlers are guarded
  edit_note  -> no finding      (ownership check controls the denial)
  list_notes -> no finding      (identity constraint in the query)

4.2 authors the sink facts the go/no-go measured as its largest miss class (11
of 23): Django ORM raw SQL, and the four families that previously had no fact
routing to them by CWE at all -- path, output_encoding, untrusted_destination,
prototype. Each entry is a documented dangerous API of the named library with
its provenance recorded inline, and rule_ids left empty because a sink fact is
not a detection rule. Flagged for maintainer review as data, given the standing
"no LLM-authored patterns" constraint. The exact-set assertion written in task
1.1 to hold this gap open is updated rather than deleted, so it still fails if a
family ever loses its seed.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>
Claude-Session: https://claude.ai/code/session_01T7XD7x5KonMdmGRkp63EQG

src/openultrasast/model/specs.py

@@ -104,8 +104,16 @@ class TaintSpec:
 class DominanceSpec:
     """What an absence family's guard-dominates-operation query matches on, for one language.
 
-    ``dischargers`` are the guards that discharge an obligation; the query asks whether one of them dominates
-    the operation on every path, which is the arbiter for the classes that never crash.
+    ``dischargers`` are every token that can evidence a discharge, drawn from four fields of a discharger
+    fact and deliberately not from the other two:
+
+        calls, decorators          an explicit guard: ``login_required``, ``check_owner``
+        identity_sources           the authenticated context: ``current_user``, ``request.user``
+        constraint_params          a field that constrains by identity: ``owner_id``, ``user_id``
+
+    ``request_sources`` and ``permissive_values`` are excluded because they describe the NEGATIVE case -- a
+    value that comes from the request discharges nothing, and a permissive literal is the bug rather than the
+    guard. Including them would let the absence arbiter read a vulnerability as its own fix.
     """
 
     family: str
@@ -167,6 +175,8 @@ def dominance_specs(*, language: str, facts: ObligationFacts | None = None) -> M
         sorted(
             {call for fact in scoped.dischargers for call in fact.calls}
             | {decorator for fact in scoped.dischargers for decorator in fact.decorators}
+            | {source for fact in scoped.dischargers for source in fact.identity_sources}
+            | {param for fact in scoped.dischargers for param in fact.constraint_params}
         )
     )
     return {"access_control": DominanceSpec(family="access_control", language=language, operations=operations, dischargers=dischargers)}