Reduce exported functions (#77) (#79)

* refactor: internalize reduction structs and gadgets in rules module

Remove public re-exports of ~30 ReductionXToY structs, 6 gadget
functions, BoolVar, LogicGadget, and JSON serialization types
(EdgeJson, NodeJson, ReductionGraphJson) from rules/mod.rs. Users
interact with reductions via the ReduceTo trait or ReductionGraph,
never referencing these structs by name.

Also remove unused ReductionColoringToILP type alias and suppress
dead_code warnings on LogicGadget fields only read in tests.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* refactor: internalize unitdiskmapping implementation details

Change internal type re-exports (CopyLine, MappingGrid, CellState,
Pattern, etc.) from pub to pub(crate) in unitdiskmapping/mod.rs.
Change alpha_tensor and pathdecomposition modules to pub(crate).

Add #[cfg(test)] guards on re-exports only needed by unit tests.
Add #[doc(hidden)] _internal module for the export_mapping_stages
example which needs these types.

Keep ksg, triangular modules and GridKind/MappingResult as pub.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* refactor: internalize polynomial/truth_table, delete unused graph_types module

- Change polynomial and truth_table modules from pub to pub(crate)
  since they are only used internally via crate:: imports.
- Delete graph_types.rs and its unit test file (zero internal imports,
  confirmed by codebase audit; actual graph types live in topology/).
- Remove truth_table integration tests from tests/suites/reductions.rs
  (equivalent coverage exists in src/unit_tests/truth_table.rs).
- Remove doc example from TruthTable since the module is now internal.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* feat: add is_valid_solution methods to graph problem types

Add public is_valid_solution(&self, config: &[usize]) -> bool methods to
all graph problem types, delegating to existing private validation helpers.
Also add cut_size method to MaxCut for computing partition cut sizes.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* feat: add is_valid_solution methods to set and specialized problems

Add public is_valid_solution methods to MaximumSetPacking,
MinimumSetCovering, BicliqueCover, CircuitSAT, and Factoring.
Each delegates to existing validation logic. PaintShop already
has count_switches and BMF is skipped per design.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* refactor: internalize validation free functions, keep as problem methods

Change standalone validation free functions (is_independent_set,
is_vertex_cover, is_clique, etc.) from pub to pub(crate) with #[cfg(test)]
for test-only functions. Functions still used in non-test code
(is_valid_coloring, is_hamiltonian_cycle, cut_size) remain pub(crate)
without #[cfg(test)].

- Change 17 validation functions from pub to pub(crate)
- Add #[cfg(test)] to 14 functions only used in tests
- Remove validation function re-exports from graph/set/specialized mod.rs
- Make submodules pub(crate) for crate-internal test access
- Update graph_models.rs imports to use full module paths

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* refactor: internalize config_to_bits and bits_to_config

Change these utility functions from pub to pub(crate) with #[cfg(test)]
since they are only used in unit tests. This reduces the public API
surface of the config module.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

* refactor: slim down prelude to essential items

Remove from prelude: config utilities, registry types, variant types,
ILP/optimization internals, NumericSize, and WeightElement. These items
remain accessible via their full module paths.

Add explicit imports to 16 examples, 2 integration test files that
previously relied on the broader prelude:
- ILP type: 13 examples + 1 test file
- K3/K2 variant types: 7 examples + 2 test files
- LinearConstraint/ObjectiveSense: 1 example + 1 test file

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

Author: GiggleLiu

examples/chained_reduction_ksat_to_mis.rs

@@ -10,6 +10,7 @@ use problemreductions::rules::{MinimizeSteps, ReductionGraph};
 use problemreductions::solvers::ILPSolver;
 use problemreductions::topology::SimpleGraph;
 use problemreductions::types::ProblemSize;
+use problemreductions::variant::K3;
 // ANCHOR_END: imports
 
 pub fn run() {

examples/export_mapping_stages.rs

@@ -8,8 +8,11 @@
 //!           cargo run --example export_mapping_stages -- petersen triangular
 
 use problemreductions::rules::unitdiskmapping::{
-    create_copylines, ksg, mis_overhead_copyline, mis_overhead_copyline_triangular, triangular,
-    CopyLine, MappingGrid,
+    _internal::{
+        create_copylines, mis_overhead_copyline, mis_overhead_copyline_triangular, CopyLine,
+        MappingGrid,
+    },
+    ksg, triangular,
 };
 use problemreductions::topology::smallgraph;
 use serde::Serialize;
@@ -102,7 +105,7 @@ fn gadget_name(idx: usize) -> String {
 // The Typst script converts to 1-indexed for comparison with Julia.
 // DO NOT add +1 here - keep 0-indexed!
 fn extract_grid_nodes(grid: &MappingGrid) -> Vec<GridNodeExport> {
-    use problemreductions::rules::unitdiskmapping::CellState;
+    use problemreductions::rules::unitdiskmapping::_internal::CellState;
     let mut nodes = Vec::new();
     let (rows, cols) = grid.size();
     for r in 0..rows {

examples/reduction_factoring_to_ilp.rs

@@ -18,6 +18,7 @@
 // Exports `docs/paper/examples/factoring_to_ilp.json` for use in paper code blocks.
 
 use problemreductions::export::*;
+use problemreductions::models::optimization::ILP;
 use problemreductions::prelude::*;
 use problemreductions::solvers::ILPSolver;
 

examples/reduction_ilp_to_qubo.rs

@@ -36,6 +36,7 @@
 // ```
 
 use problemreductions::export::*;
+use problemreductions::models::optimization::{ILP, LinearConstraint, ObjectiveSense};
 use problemreductions::prelude::*;
 
 pub fn run() {

examples/reduction_kcoloring_to_ilp.rs

@@ -16,10 +16,12 @@
 // Exports `docs/paper/examples/kcoloring_to_ilp.json` and `kcoloring_to_ilp.result.json`.
 
 use problemreductions::export::*;
+use problemreductions::models::optimization::ILP;
 use problemreductions::prelude::*;
 use problemreductions::solvers::ILPSolver;
 use problemreductions::topology::small_graphs::petersen;
 use problemreductions::topology::{Graph, SimpleGraph};
+use problemreductions::variant::K3;
 
 pub fn run() {
     // 1. Create KColoring instance: Petersen graph (10 vertices, 15 edges) with 3 colors, χ=3

examples/reduction_kcoloring_to_qubo.rs

@@ -32,6 +32,7 @@ use problemreductions::export::*;
 use problemreductions::prelude::*;
 use problemreductions::topology::small_graphs::house;
 use problemreductions::topology::{Graph, SimpleGraph};
+use problemreductions::variant::K3;
 
 pub fn run() {
     println!("=== K-Coloring -> QUBO Reduction ===\n");

examples/reduction_ksatisfiability_to_qubo.rs

@@ -38,6 +38,7 @@
 
 use problemreductions::export::*;
 use problemreductions::prelude::*;
+use problemreductions::variant::K3;
 
 pub fn run() {
     println!("=== K-Satisfiability (3-SAT) -> QUBO Reduction ===\n");

examples/reduction_maximumclique_to_ilp.rs

@@ -15,6 +15,7 @@
 // Exports `docs/paper/examples/maximumclique_to_ilp.json` and `maximumclique_to_ilp.result.json`.
 
 use problemreductions::export::*;
+use problemreductions::models::optimization::ILP;
 use problemreductions::prelude::*;
 use problemreductions::topology::small_graphs::octahedral;
 use problemreductions::topology::{Graph, SimpleGraph};

examples/reduction_maximumindependentset_to_ilp.rs

@@ -14,6 +14,7 @@
 // Exports `docs/paper/examples/maximumindependentset_to_ilp.json` and `maximumindependentset_to_ilp.result.json`.
 
 use problemreductions::export::*;
+use problemreductions::models::optimization::ILP;
 use problemreductions::prelude::*;
 use problemreductions::topology::small_graphs::petersen;
 use problemreductions::topology::{Graph, SimpleGraph};

examples/reduction_maximummatching_to_ilp.rs

@@ -14,6 +14,7 @@
 // Exports `docs/paper/examples/maximummatching_to_ilp.json` and `maximummatching_to_ilp.result.json`.
 
 use problemreductions::export::*;
+use problemreductions::models::optimization::ILP;
 use problemreductions::prelude::*;
 use problemreductions::topology::small_graphs::petersen;
 use problemreductions::topology::{Graph, SimpleGraph};