fix: Allow COPT solution parsing for IMPRECISE status (#466)

* fix: Allow COPT solution parsing for IMPRECISE status

Add 'numerical' and 'imprecise' as proper TerminationCondition enum values
and map them to SolverStatus.ok to enable solution extraction for both
COPT solver statuses. 

This fixes issue #460 where COPT solutions with IMPRECISE status were
not being parsed, even though COPT developers confirmed solutions
should be available for OK, NUMERICAL, and IMPRECISE statuses.

Co-authored-by: Fabian Hofmann <[email protected]>

* revert: Remove 'numerical' termination condition, keep only 'imprecise'

Remove 'numerical' enum value and mapping from STATUS_TO_TERMINATION_CONDITION_MAP while preserving the 'imprecise' additions for COPT solver compatibility.

Co-authored-by: Fabian Hofmann <[email protected]>

---------

Co-authored-by: claude[bot] <209825114+claude[bot]@users.noreply.github.com>
Co-authored-by: Fabian Hofmann <[email protected]>

Author: FabianHofmann

linopy/constants.py

@@ -106,6 +106,7 @@ class TerminationCondition(Enum):
     iteration_limit = "iteration_limit"
     terminated_by_limit = "terminated_by_limit"
     suboptimal = "suboptimal"
+    imprecise = "imprecise"
 
     # WARNING
     unbounded = "unbounded"
@@ -141,6 +142,7 @@ def process(
         TerminationCondition.time_limit,
         TerminationCondition.terminated_by_limit,
         TerminationCondition.suboptimal,
+        TerminationCondition.imprecise,
     ],
     SolverStatus.warning: [
         TerminationCondition.unbounded,