Add MOA.AllowInnerInterrupt to support interrupting an inner solve

[odow]

Closes #187

With this PR:

julia> using Revise

julia> using JuMP, HiGHS

julia> import MultiObjectiveAlgorithms as MOA

julia> begin
           model = Model(() -> MOA.Optimizer(HiGHS.Optimizer))
           N = 10_000
           set_attribute(model, MOA.SilentInner(), false)
           set_attribute(model, MOA.ComputeIdealPoint(), false)
           set_attribute(model, MOA.AllowInnerInterrupt(), true)
           w, C = rand(N), rand(3, N)
           @variable(model, 0 <= x[1:N] <= 3, Int)
           @constraint(model, w' * x <= 0.1 * N)
           @objective(model, Max, C * x)
           optimize!(model)
       end
-----------------------------------------------------------
        MultiObjectiveAlgorithms.jl
-----------------------------------------------------------
Algorithm: Nothing
-----------------------------------------------------------
solve #     Obj. 1       Obj. 2       Obj. 3       Time    
-----------------------------------------------------------
Running HiGHS 1.13.1 (git hash: 1d267d97c): Copyright (c) 2026 under Apache 2.0 license terms
Using BLAS: blastrampoline 
MIP has 1 row; 10000 cols; 10000 nonzeros; 10000 integer variables (0 binary)
Coefficient ranges:
  Matrix  [2e-05, 1e+00]
  Cost    [3e-05, 1e+00]
  Bound   [3e+00, 3e+00]
  RHS     [1e+03, 1e+03]
WARNING: Problem has some excessively small costs
Presolving model
1 rows, 10000 cols, 10000 nonzeros  0s
1 rows, 10000 cols, 10000 nonzeros  0s
Presolve reductions: rows 1(-0); columns 10000(-0); nonzeros 10000(-0) - Not reduced

Solving MIP model with:
   1 row
   10000 cols (0 binary, 10000 integer, 0 implied int., 0 continuous, 0 domain fixed)
   10000 nonzeros

Src: B => Branching; C => Central rounding; F => Feasibility pump; H => Heuristic;
     I => Shifting; J => Feasibility jump; L => Sub-MIP; P => Empty MIP; R => Randomized rounding;
     S => Solve LP; T => Evaluate node; U => Unbounded; X => User solution; Y => HiGHS solution;
     Z => ZI Round; l => Trivial lower; p => Trivial point; u => Trivial upper; z => Trivial zero

        Nodes      |    B&B Tree     |            Objective Bounds              |  Dynamic Constraints |       Work      
Src  Proc. InQueue |  Leaves   Expl. | BestBound       BestSol              Gap |   Cuts   InLp Confl. | LpIters     Time

 z       0       0         0   0.00%   inf             -0                 Large        0      0      0         0     0.8s
 J       0       0         0   0.00%   inf             2.987582924        Large        0      0      0         0     0.8s
 S       0       0         0   0.00%   15110.711809    4421.126918      241.78%        0      0      0         0     0.8s
         1       0         1 100.00%   4421.480061     4421.126918        0.01%        0      0      0         0     0.8s

Solving report
  Status            Optimal
  Primal bound      4421.126918
  Dual bound        4421.48006064
  Gap               0.00799% (tolerance: 0.01%)
  P-D integral      28.0956224817
  Solution status   feasible
                    4421.126918 (objective)
                    0 (bound viol.)
                    0 (int. viol.)
                    0 (row viol.)
  Timing            0.80
  Max sub-MIP depth 0
  Nodes             1
  Repair LPs        0
  LP iterations     0
    1    4.42113e+03  3.22219e+03  3.40196e+03  8.90220e-01
MIP has 2 rows; 10000 cols; 20000 nonzeros; 10000 integer variables (0 binary)
Coefficient ranges:
  Matrix  [2e-05, 1e+00]
  Cost    [2e-05, 1e+00]
  Bound   [3e+00, 3e+00]
  RHS     [1e+03, 4e+03]
WARNING: Problem has some excessively small costs
Presolving model
2 rows, 10000 cols, 20000 nonzeros  0s
2 rows, 10000 cols, 20000 nonzeros  0s
Presolve reductions: rows 2(-0); columns 10000(-0); nonzeros 20000(-0) - Not reduced

Solving MIP model with:
   2 rows
   10000 cols (0 binary, 10000 integer, 0 implied int., 0 continuous, 0 domain fixed)
   20000 nonzeros

Src: B => Branching; C => Central rounding; F => Feasibility pump; H => Heuristic;
     I => Shifting; J => Feasibility jump; L => Sub-MIP; P => Empty MIP; R => Randomized rounding;
     S => Solve LP; T => Evaluate node; U => Unbounded; X => User solution; Y => HiGHS solution;
     Z => ZI Round; l => Trivial lower; p => Trivial point; u => Trivial upper; z => Trivial zero

        Nodes      |    B&B Tree     |            Objective Bounds              |  Dynamic Constraints |       Work      
Src  Proc. InQueue |  Leaves   Expl. | BestBound       BestSol              Gap |   Cuts   InLp Confl. | LpIters     Time

         0       0         0   0.00%   14879.292791    -inf                 inf        0      0      0         0     0.6s
         0       0         0   0.00%   3255.055537     -inf                 inf        0      0      0         9     0.6s
 C       0       0         0   0.00%   3255.055537     3233.412133        0.67%        0      0      9         9     0.6s
 L       0       0         0   0.00%   3255.055537     3233.699126        0.66%        0      0      9         9     0.9s

63.5% inactive integer columns, restarting
^C         0       0         0   0.00%   3255.055537     3233.699126        0.66%        0      0      0       292     1.3s

Solving report
  Status            Interrupted by user
  Primal bound      3233.69912594
  Dual bound        3255.0555372
  Gap               0.66% (tolerance: 0.01%)
  P-D integral      0.00452400191569
  Solution status   feasible
                    3233.69912594 (objective)
                    0 (bound viol.)
                    0 (int. viol.)
                    0 (row viol.)
  Timing            1.32
  Max sub-MIP depth 6
  Nodes             0
  Repair LPs        0
  LP iterations     292
                    0 (strong br.)
                    0 (separation)
                    283 (heuristics)
    2    4.42121e+03  3.23370e+03  3.40720e+03  2.22012e+00
-----------------------------------------------------------
termination_status: INTERRUPTED
result_count: 1

Total solve time:          2.22026e+00
Time spent in subproblems: 2.20962e+00 (100%)
Number of subproblems:     2
-----------------------------------------------------------

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.76%. Comparing base (1a25bab) to head (9df6525).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master     #188   +/-   ##
=======================================
  Coverage   99.76%   99.76%           
=======================================
  Files          12       12           
  Lines        1290     1301   +11     
=======================================
+ Hits         1287     1298   +11     
  Misses          3        3           

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[sandyspiers]

Looks great, works exactly as expected. Thanks very much!!