[Critical] Fix reduction result recovery and reference validation contracts

[isPANN]

Summary

Fix reduction result recovery, model validation, and reference-solver correctness while retaining the existing Problem, SolutionAggregate, and typed witness/value reduction interfaces.

API and behavior changes

• Keep witness extraction and completed aggregate mapping separate. Register value mappings beside their implementations and reuse the constructed reduction for both mappings. Dynamic aggregate extraction is fallible; chains expose extract_value.
• Enforce decision thresholds during recovery. Established target or intermediate infeasibility propagates without a witness; extraction errors and worker failures remain errors, not NO answers.
• Use pred extract bundle.json --result result.json with explicit feasible, optimal, infeasible, or complete status. Optional witness evaluations must match the model's evaluation. A candidate evaluation does not establish optimality or exhaustive NO.
• Model decision thresholds explicitly with Decision<P>. Direct bounded OpenShopScheduling and LongestCircuit ILP encodings add a bound constraint and use a zero objective; their optimization versions retain their objectives.
• Enforce construction constraints through Rust and JSON, with explicit numeric and representation errors. Correct rule edge cases, signed TSP costs, and malformed witness extraction.
• Make CVP integer-only with squared-distance Min<i64> values and the coefficient variant key. Persist QUBO as num_vars plus sparse entries. Register KColoring KN/K2/K3 variants and provide a direct bipartite solver for K2.
• Isolate HiGHS conversion and execution in a concrete adapter; native integer ILPs go directly to it. Numerical solver guarantees remain subject to HiGHS tolerances.
• Remove the total-cardinality requirement from Cartesian enumeration. Use existing Lehmer decoding for CyclicOrdering, Betweenness, and MinimumCodeGenerationUnlimitedRegisters instead of enumerating invalid position vectors.

Core Problem and solver return interfaces are not migrated. Model-specific getters/parameters, dynamic extraction signatures, persisted formats, and supported variants do change; this is a critical API review. P → Decision<P> remains a Turing edge (binary search over the decision bound).

Scope

Against main at head 31bdb314: 404 files changed, 14,058 additions, 4,712 deletions. No website changes. The obsolete SteinerTreeInGraphs removal is already in main and is not part of this diff.

Validation

• CI at 31bdb314: Test, Clippy, Rustfmt, coverage, RISC-V, Windows x86_64, and macOS ARM64 checks passed; Codecov checks passed.
• Local all-feature workspace library/binary/integration tests at ef634c2b: 6,727 passed, 2 ignored. Workspace Clippy with warnings denied, formatting, and paper build passed.
• After the test-only simplification at 67715f12: all 19 solver-registry tests passed.
• Local follow-up recovered all 597 original corpus recovery-error cases as infeasible with unchanged source truth.
• Two previously timed-out full-bundle examples passed locally: Partition → bounded OpenShopScheduling in 0.80 s (NO), and DecisionMinimumVertexCover → HamiltonianCircuit in 0.57 s (YES with a valid recovered cover). These are debug-build examples, not HPC-wide performance claims.

[codecov]

Codecov Report

❌ Patch coverage is 98.03423% with 85 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.75%. Comparing base (5a35ce7) to head (8291c5b).

Files with missing lines	Patch %	Lines
src/solvers/ilp/adapter.rs	91.61%	14 Missing ⚠️
src/rules/ksatisfiability_qubo.rs	71.42%	10 Missing ⚠️
src/rules/coloring_qubo.rs	55.00%	9 Missing ⚠️
src/rules/satisfiability_maximum2satisfiability.rs	60.00%	6 Missing ⚠️
src/solvers/customized/solver.rs	81.81%	6 Missing ⚠️
...s/misc/consistency_of_database_frequency_tables.rs	83.33%	4 Missing ⚠️
src/rules/ksatisfiability_timetabledesign.rs	73.33%	4 Missing ⚠️
...rules/ksatisfiability_simultaneousincongruences.rs	76.92%	3 Missing ⚠️
src/rules/sat_ksat.rs	88.46%	3 Missing ⚠️
src/registry/dyn_problem.rs	83.33%	2 Missing ⚠️
... and 21 more

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1171      +/-   ##
==========================================
+ Coverage   96.22%   96.75%   +0.52%     
==========================================
  Files        1070     1069       -1     
  Lines      133605   138821    +5216     
==========================================
+ Hits       128564   134312    +5748     
+ Misses       5041     4509     -532     

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