area_context v2 + Maps place verification (server-26#36, #37)

#36 — the correction pass shipped in 58efdbd was right, its reference-data
shape was not. One shape now, at both scopes, every field nullable:

  area_context: { municipality?, county?, state?,
                  center?, radius_km?, resolved_from?, resolved_at?,
                  local_knowledge?: [{term, meaning}] }

`state` closes the ambiguity that made "Ossining" a national guess.
`local_knowledge` replaces roads[]/landmarks[], which could not hold
intersections, schools or nicknames and carried no meanings — `11-X-ray` is
useless alone, `11-X-ray — MTA PD patrol unit` is what a corrector can act on.
Pre-#36 roads[]/landmarks[] are read forward as bare terms so nothing an
operator already entered is lost.

Nullability is the mechanism: which scope gets filled is the operator's
declaration of how homogeneous the system is. One town — fill it once at system
level. Statewide — leave it blank and fill each talkgroup.

The backend owns the derived anchor. PUT /systems/{id} merges config.talkgroups[]
against what is stored instead of writing the client's blob verbatim, which
would have erased the anchor and the pending queue — the same defect as the
ten_codes wipe.

#37 — Maps as a verifier, not as prompt stuffing. The corrector emits its
location nouns; each is geocoded against the talkgroup's anchor, and on a miss
we look for a sound-alike that does resolve there, correct to it, and propose
{term, meaning} to that talkgroup. Cost scales with location nouns, not calls.

No anchor means SKIP. An area too wide to discriminate stores no anchor at all,
because a statewide radius would confirm anything inside it — verification that
passes everything is worse than none, since it reads as a check in the data.

Also re-anchors _geocode_location, which rejected results >40km from the NODE
(server-26#6). An antenna is not a jurisdiction; distance-from-node was always
a stand-in for the anchor and is now only the fallback.

The induction loop proposes at talkgroup level and never promotes. Blast
radius: a wrong term on a channel misleads that channel, the same term
system-wide misleads one 400km away on a statewide system.

38 new tests; 240 pass. Frontend typechecks clean.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

drb-c2-core/app/models.py

@@ -78,6 +78,49 @@ class CommandPayload(BaseModel):
 # Systems
 # ---------------------------------------------------------------------------
 
+class LocalKnowledgeEntry(BaseModel):
+    """A local name and what it is. Both scopes, one shape (server-26#36)."""
+    term: str
+    meaning: Optional[str] = None
+
+
+class AreaContextBody(BaseModel):
+    """
+    Ground truth about the area a system or talkgroup covers.
+
+    Every field is nullable on purpose: which SCOPE an operator fills is their
+    declaration of how homogeneous the system is. A single-municipality system
+    is described once at system level and inherited by every talkgroup; a
+    statewide one is left null there and described per talkgroup. See
+    `internal/area_context.py` for the merge rules and the anchor.
+
+    `center`/`radius_km`/`resolved_from`/`resolved_at` are absent here by
+    design — the backend geocodes and writes those. A client that sends them is
+    ignored.
+    """
+    municipality: Optional[str] = None
+    county: Optional[str] = None
+    state: Optional[str] = None
+    local_knowledge: List[LocalKnowledgeEntry] = []
+
+
+class TalkgroupEntry(BaseModel):
+    """
+    One entry in `config.talkgroups[]`.
+
+    Declared so the talkgroup copy of `area_context` stops being unvalidated
+    JSON riding inside the config blob — it is the same shape as the system's
+    and gets the same validator (server-26#36).
+    """
+    model_config = {"extra": "allow"}
+
+    id: int
+    name: str = ""
+    tag: str = "other"
+    vocabulary: List[str] = []
+    area_context: Optional[AreaContextBody] = None
+
+
 class SystemRecord(BaseModel):
     system_id: str
     org_id: Optional[str] = None
@@ -86,9 +129,10 @@ class SystemRecord(BaseModel):
     config: Dict[str, Any] = {}     # OP25-compatible config blob
     ten_codes: Dict[str, str] = {}  # {"10-10": "Commercial Alarm", ...}
     # Ground truth about the area this system covers, fed to the transcript
-    # corrector (server-26#36): {municipality, county, roads[], landmarks[]}.
-    # Per-talkgroup overrides live inside config.talkgroups[] and rank ABOVE
-    # this, so a multi-county system can narrow per channel.
+    # corrector and the place verifier (server-26#36 / #37). Shape is
+    # AreaContextBody plus the backend-owned anchor. Per-talkgroup overrides
+    # live inside config.talkgroups[] and rank ABOVE this, so a multi-county
+    # system narrows per channel rather than replacing this wholesale.
     area_context: Dict[str, Any] = {}