feat: Decision wrapper for optimization→decision conversion

[GiggleLiu]

Summary

• Add generic Decision<P> wrapper that converts optimization problems (Min/Max valued) to decision problems (Or valued) via a bound parameter
• Add OptimizationValue trait abstracting over Min<V>/Max<V> with meets_bound() semantics
• Add ReduceToAggregate impl for Decision<P> → P (solve optimization, compare to bound)
• Add golden-section search solver that recovers optima by querying Decision<P> instances
• Replace hand-written VertexCover with Decision<MinimumVertexCover> (aliases VertexCover/VC preserved)
• Fix proc macro extract_type_name() to handle Decision<T> nested generics
• Register concrete variants for Decision<MinimumVertexCover> and Decision<MinimumDominatingSet>

Closes #998

Test plan

• cargo test optimization_value — 8 tests for OptimizationValue trait
• cargo test test_decision — 9 tests for Decision<P> struct, solver, serialization, aggregate reduction
• cargo test test_golden_section — 3 tests for golden-section search solver
• make check — full suite (fmt + clippy + test)
• Verify pred show VertexCover and pred show VC still resolve (alias migration)

🤖 Generated with Claude Code

[Copilot]

Pull request overview

This PR introduces a generic Decision<P> wrapper to convert optimization problems (Min/Max) into decision problems (Or) via a bound, migrates the VertexCover decision model to this wrapper while preserving CLI aliases, and adds a decision-query-based search utility plus registry/docs updates to reflect the new decision types.

Changes:

• Add OptimizationValue + Decision<P> (with ReduceToAggregate) to support generic optimization→decision conversion and aggregate edges back to the inner optimization problem.
• Register concrete decision variants/schemas for Decision<MinimumVertexCover<SimpleGraph,i32>> and Decision<MinimumDominatingSet<SimpleGraph,i32>>, removing the bespoke VertexCover model while preserving VertexCover/VC CLI aliases.
• Add a decision-query-based solver utility (named “golden section”) and update CLI/docs/tests to validate registry, examples, and alias resolution.

Reviewed changes

Copilot reviewed 26 out of 26 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
src/types.rs	Adds OptimizationValue trait + Min/Max implementations; wires new unit test module.
src/models/decision.rs	Introduces generic Decision<P> wrapper, DecisionProblemMeta, and aggregate reduction Decision<P> → P.
src/models/mod.rs	Exposes decision module and re-exports Decision; removes VertexCover re-export.
src/models/graph/minimum_vertex_cover.rs	Registers DecisionMinimumVertexCover schema/variant + aggregate edge; adds example-db spec.
src/models/graph/minimum_dominating_set.rs	Registers DecisionMinimumDominatingSet schema/variant + aggregate edge.
src/models/graph/maximum_independent_set.rs	Registers DecisionProblemMeta for MIS (for decision-query tooling/tests).
src/models/graph/mod.rs	Removes vertex_cover module export; adds decision-MVC example specs into example-db aggregation.
src/models/graph/vertex_cover.rs	Removes bespoke VertexCover decision model implementation.
src/solvers/golden_section.rs	Adds decision-query search helper (implemented as integer binary search).
src/solvers/mod.rs	Exposes the new golden_section solver module.
src/unit_tests/types_optimization_value.rs	Adds tests for OptimizationValue::meets_bound semantics.
src/unit_tests/models/decision.rs	Adds tests for Decision<P> evaluation, serde roundtrip, and aggregate reduction.
src/unit_tests/solvers/golden_section.rs	Adds tests validating decision-query search recovers optima and handles invalid intervals.
src/unit_tests/registry/schema.rs	Adds tests asserting decision schemas/variants are registered and VertexCover legacy schema removed.
src/unit_tests/reduction_graph.rs	Adds tests asserting direct aggregate edges from decision wrappers to optimization problems.
src/unit_tests/models/graph/vertex_cover.rs	Removes tests for the deleted bespoke VertexCover model.
src/unit_tests/example_db.rs	Adds example-db test coverage for DecisionMinimumVertexCover example instance.
problemreductions-macros/src/lib.rs	Fixes proc-macro type-name extraction to handle Decision<T> nested generics; adds tests.
problemreductions-cli/src/problem_name.rs	Updates alias resolution tests so VertexCover/VC resolve to DecisionMinimumVertexCover.
problemreductions-cli/src/mcp/prompts.rs	Updates default prompt example to use DecisionMinimumVertexCover.
problemreductions-cli/src/commands/create/schema_support.rs	Updates help-example fallback strings to include DecisionMinimumVertexCover.
problemreductions-cli/src/commands/create.rs	Adds random generation path for DecisionMinimumVertexCover; removes VertexCover random generation.
problemreductions-cli/src/cli.rs	Updates “Flags by problem type” help text to list DecisionMinimumVertexCover.
docs/paper/reductions.typ	Updates paper definitions and helper logic to support nested inner for decision-wrapped instances.
docs/plans/2026-04-06-decision-wrapper-plan.md	Adds implementation plan documenting steps/tests for the decision wrapper work.
docs/plans/2026-04-06-decision-wrapper-design.md	Adds design spec documenting rationale, architecture, and migration details.

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[Copilot]

ProblemSchemaEntry for DecisionMinimumVertexCover declares top-level fields graph/weights/bound, but the actual serde shape of Decision<MinimumVertexCover<...>> is { inner: { graph, weights }, bound }. This mismatch will break schema-driven CLI creation (pred create DecisionMinimumVertexCover --graph ... --weights ... --bound ...) because the variant factory will fail to deserialize the generated JSON. Consider either (a) teaching Decision<P> to deserialize from the flattened form used by the schema/CLI, or (b) changing schema-driven creation/schema fields to match the nested inner structure (or special-casing this canonical in the CLI create path).

Suggested change

	FieldInfo { name: "graph", type_name: "G", description: "The underlying graph G=(V,E)" },
	FieldInfo { name: "weights", type_name: "Vec<W>", description: "Vertex weights w: V -> R" },
	FieldInfo {
	name: "inner",
	type_name: "MinimumVertexCover<G, W>",
	description: "The optimization problem payload containing the graph G=(V,E) and vertex weights w: V -> R",
	},

[Copilot]

Same issue as DecisionMinimumVertexCover: this schema declares graph/weights/bound as top-level fields, but Decision<MinimumDominatingSet<...>> serializes as { inner: { ... }, bound }. As a result, schema-driven CLI creation for DecisionMinimumDominatingSet will generate the wrong JSON shape and the variant factory will reject it. Align the schema/CLI creation with the actual serde structure, or make Decision<P> accept both shapes on deserialization.

Suggested change

	FieldInfo { name: "graph", type_name: "G", description: "The underlying graph G=(V,E)" },
	FieldInfo { name: "weights", type_name: "Vec<W>", description: "Vertex weights w: V -> R" },
	FieldInfo { name: "bound", type_name: "i32", description: "Decision bound (maximum allowed dominating-set cost)" },
	FieldInfo {
	name: "inner",
	type_name: "MinimumDominatingSet<SimpleGraph, i32>",
	description: "The underlying minimum dominating set instance",
	},
	FieldInfo {
	name: "bound",
	type_name: "i32",
	description: "Decision bound (maximum allowed dominating-set cost)",
	},

[Copilot]

The CLI help now advertises DecisionMinimumVertexCover --graph, --weights, --bound, but schema-driven creation currently constructs JSON using the schema field names (top-level graph/weights/bound). Since Decision<...> deserializes from { inner: {...}, bound }, pred create DecisionMinimumVertexCover --graph ... --weights ... --bound ... will fail unless the model/serde or CLI creation path is updated to match.

Suggested change

	DecisionMinimumVertexCover --graph, --weights, --bound
	DecisionMinimumVertexCover use JSON input ({\"inner\": {...}, \"bound\": ...})

[Copilot]

VertexCover was removed from the public Rust re-exports (and the model file was deleted), which is a breaking change for library users who construct problemreductions::models::graph::VertexCover. If you intend to preserve the Rust API as well as the CLI alias, consider adding a public type alias (e.g., pub type VertexCover<...> = Decision<MinimumVertexCover<...>>) or documenting this as a breaking change in release notes.

[Copilot]

golden_section is implemented as a monotone binary search over integer bounds (midpoint halving), not golden-section search. This is likely fine functionally, but the module/function naming and top-level docstring are misleading and make the algorithm harder to reason about later. Consider renaming to binary_search_decision (or similar) or updating the docs to match the actual approach.

[codecov]

Codecov Report

❌ Patch coverage is 93.25843% with 36 lines in your changes missing coverage. Please review.
✅ Project coverage is 98.11%. Comparing base (90fcc85) to head (72c2d5d).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
src/models/decision.rs	71.05%	22 Missing ⚠️
src/models/graph/minimum_dominating_set.rs	68.96%	9 Missing ⚠️
src/rules/registry.rs	50.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1014      +/-   ##
==========================================
- Coverage   98.14%   98.11%   -0.03%     
==========================================
  Files         920      923       +3     
  Lines       95494    95900     +406     
==========================================
+ Hits        93723    94094     +371     
- Misses       1771     1806      +35     

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