fix: prevent truncated Ollama answers

docs/API_CONTRACTS.md

@@ -1637,4 +1637,7 @@ metrics from PostGIS and includes dated observations only for persisted
 temporal series. Geometry is not sent to Ollama. The response contains the
 answer, used model, scope label, context metrics, discovered temporal series,
 source dataset ids and warnings. Missing measurements remain unavailable;
-specifically, no water volume is inferred from 2D water geometry.
+specifically, no water volume is inferred from 2D water geometry. The backend
+sets an explicit Ollama context window and returns
+`OLLAMA_RESPONSE_TRUNCATED` instead of accepting a response with
+`done_reason=length` as a complete answer.

docs/CODEX_EXECUTION_LOG.md

@@ -8389,7 +8389,7 @@ Validation evidence:
 - Focused temporal, source, Ollama, navigation and Unraid regression tests
   passed, including direct coverage for multi-metric history and DockerMan host
   mapping.
-- Full readiness passed 615 backend tests, backend compilation, 91 documented
+- Full readiness passed 617 backend tests, backend compilation, 91 documented
   API routes, one Alembic head, frontend TypeScript typecheck/build and all
   shell syntax gates.
 - Tower deployment passed the all-in-one container health check, live PostGIS
@@ -8403,6 +8403,15 @@ Validation evidence:
   message keys now use a session-local monotonic id generator; no persisted or
   security-sensitive identity depends on it. Typecheck, production build and
   full readiness reran successfully.
+- The regional operator then reused the five governed forest snapshots and
+  imported 15 new authoritative snapshots: water, built functions and
+  transport for 2013, 2016, 2019, 2022 and 2025. A live exact-Area Mol water
+  comparison returned 606.16 ha in 2013 and 641.75 ha in 2025 across all five
+  observations; the API retained the 10 m raster and object-lineage warnings.
+- Browser QA also reproduced an Ollama `done_reason=length`: the previous
+  implicit 4096-token context left only 86 tokens after a 4010-token grounded
+  prompt. GeoIntel now requests a configurable 16,384-token context and rejects
+  any future length-truncated response instead of presenting a partial answer.
 
 Known limitations:
 - Water volume remains unavailable until a governed depth/bathymetry source is