Replace Polynomial overhead system with Expr AST

[GiggleLiu]

Summary

• Introduce Expr AST type (src/expr.rs) replacing Polynomial for reduction overhead expressions
• Add Pratt expression parser in proc macro crate for compile-time parsing of overhead strings
• New #[reduction] syntax: overhead = { field = "expression" } instead of inline poly!() calls
• Add inherent size getter methods to all 21 problem types
• Remove problem_size_names()/problem_size_values() from Problem trait
• Remove source_size_names_fn/target_size_names_fn from ReductionEntry
• Delete Polynomial type and poly! macro entirely
• Update CLI, MCP server, and documentation

Test plan

• All 1,613 tests pass (1,474 unit + 96 integration + 43 doc)
• make check (fmt + clippy + test) passes
• make mcp-test passes
• make examples and make export-schemas succeed
• No new clippy warnings

🤖 Generated with Claude Code

[GiggleLiu]

remove this file.

[Copilot]

Pull request overview

This PR replaces the Polynomial-based reduction overhead system with a more general Expr AST representation. The new system uses compile-time expression parsing via a Pratt parser in the proc macro, replacing the runtime-only poly! macro and trait-based problem_size_names()/problem_size_values() methods with inherent getters on problem types.

Changes:

• Introduced Expr AST type with support for arithmetic operations, exponentiation, exp, log, and sqrt
• Added Pratt parser in proc macro crate for compile-time parsing of overhead expression strings
• Replaced #[reduction(overhead = { ReductionOverhead::new(...) })] syntax with overhead = { field = "expression" }
• Added inherent size getter methods (e.g., num_vertices(), num_edges()) to all 21 problem types
• Removed problem_size_names()/problem_size_values() from Problem trait and all implementations
• Deleted entire Polynomial type, Monomial type, and poly! macro
• Updated export schema to include both AST (expr) and display string (formula) fields

Reviewed changes

Copilot reviewed 85 out of 85 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/expr.rs	New Expr AST enum with eval, substitute, variables, and Display
problemreductions-macros/src/parser.rs	New Pratt parser for overhead expression strings
problemreductions-macros/src/lib.rs	Updated #[reduction] macro to support new syntax alongside legacy
src/models/**/*.rs	Added inherent getter methods, removed problem_size_* trait methods from all 21 problem types
src/rules/**/*.rs	Migrated all reductions to new overhead syntax
src/rules/registry.rs	Changed ReductionOverhead to use Expr instead of Polynomial, removed size name fields from ReductionEntry
src/polynomial.rs	Deleted entire file (340 lines)
src/unit_tests/polynomial.rs	Deleted (180 tests)
src/unit_tests/expr.rs	Added comprehensive tests for new Expr type
src/export.rs	Updated schema: OverheadEntry now has expr and formula fields
problemreductions-cli/**	Updated CLI and MCP to use size_field_names() from reduction graph
docs/**	Updated design docs and CLAUDE.md to reflect new system

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[GiggleLiu]

@isPANN Please carefully check and verify this design document. Any thoughts?

[codecov]

Codecov Report

❌ Patch coverage is 70.57292% with 113 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.46%. Comparing base (9671215) to head (cc8bebb).
⚠️ Report is 16 commits behind head on main.

Files with missing lines	Patch %	Lines
src/expr.rs	77.65%	21 Missing ⚠️
src/models/set/maximum_set_packing.rs	0.00%	7 Missing ⚠️
src/models/graph/kcoloring.rs	0.00%	6 Missing ⚠️
src/models/graph/max_cut.rs	0.00%	6 Missing ⚠️
src/models/graph/maximal_is.rs	0.00%	6 Missing ⚠️
src/models/graph/maximum_clique.rs	0.00%	6 Missing ⚠️
src/models/graph/maximum_independent_set.rs	0.00%	6 Missing ⚠️
src/models/graph/maximum_matching.rs	0.00%	6 Missing ⚠️
src/models/graph/minimum_dominating_set.rs	0.00%	6 Missing ⚠️
src/models/graph/minimum_vertex_cover.rs	0.00%	6 Missing ⚠️
... and 9 more

❌ Your patch status has failed because the patch coverage (70.57%) is below the target coverage (95.00%). You can increase the patch coverage or adjust the target coverage.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #99      +/-   ##
==========================================
+ Coverage   96.36%   96.46%   +0.10%     
==========================================
  Files         197      196       -1     
  Lines       27214    26620     -594     
==========================================
- Hits        26224    25679     -545     
+ Misses        990      941      -49     

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