Add the spec-aligned EstimationReport Pydantic domain model with
multi-dimensional estimation output: cost range (min/max USD),
expected steps and child plans, rollback risk (0.0-1.0), estimated
duration in minutes, confidence score (0.0-1.0), rationale, and
optional historical basis (plan IDs).

Add estimation_produced to the DecisionType enum and STRATEGIZE_TYPES
frozenset for recording estimation results in the decision tree.

Add Alembic migration m6_006 that adds the estimation_report TEXT
column to v3_plans and updates the ck_decisions_type CHECK constraint
to include the new decision type.

Update Plan domain model and database ORM layer (models.py and
repositories.py) to serialize/deserialize EstimationReport via JSON.

Update existing consolidated_decision.feature and decision model
Robot helper to expect 12 decision types (was 11).

Add comprehensive BDD tests (20 scenarios in estimation_report.feature)
and Robot Framework integration tests (6 test cases) covering creation,
serialization round-trip, validation constraints, immutability, and
DecisionType membership.

ISSUES CLOSED: #649

@@ -962,1 +972,4 @@
+                raw_estimation_report
+            )
+
         return Plan(