Fix #296: [Model] UndirectedTwoCommodityIntegralFlow

[GiggleLiu]

Summary

• add the issue [Model] UndirectedTwoCommodityIntegralFlow #296 implementation plan for Undirected Two-Commodity Integral Flow
• outline the Batch 1 model/CLI/example work and the separate Batch 2 paper task

Fixes #296

[codecov]

Codecov Report

❌ Patch coverage is 98.74608% with 4 lines in your changes missing coverage. Please review.
✅ Project coverage is 96.97%. Comparing base (a977548) to head (25269e7).
⚠️ Report is 1 commits behind head on main.

Files with missing lines	Patch %	Lines
...ls/graph/undirected_two_commodity_integral_flow.rs	97.84%	4 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #658      +/-   ##
==========================================
+ Coverage   96.96%   96.97%   +0.01%     
==========================================
  Files         275      277       +2     
  Lines       36843    37161     +318     
==========================================
+ Hits        35724    36038     +314     
- Misses       1119     1123       +4     

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[GiggleLiu]

Implementation Summary

Changes

• Added the new UndirectedTwoCommodityIntegralFlow model with schema registration, variant declaration, canonical example, example-db exports, CLI create/help support, paper entry, and trait-consistency wiring.
• Added model and CLI coverage for the canonical instance, registry visibility, example exports, and create-command behavior.
• Tightened post-review edge-case handling for very large capacities by using checked/wider arithmetic in evaluate() and by returning user-facing CLI validation errors for invalid terminals/capacities instead of panicking.

Deviations from Plan

• Review surfaced numeric-overflow and CLI-validation edge cases that were not explicit in the initial plan; these were fixed before finalizing the branch.

Open Questions

• None.

[Copilot]

Pull request overview

Adds the UndirectedTwoCommodityIntegralFlow graph satisfaction model (Fixes #296) and wires it through the library registry, example DB, CLI, and docs/paper so it shows up as a first-class problem type across the project.

Changes:

• Introduces UndirectedTwoCommodityIntegralFlow model implementation (schema registration, evaluation logic, variant declaration, canonical example spec).
• Adds unit tests + example-db fixture entry for the model and updates trait-consistency checks.
• Extends the CLI (list, show, create) and regenerates docs JSON / paper references + section for the new model.

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
src/models/graph/undirected_two_commodity_integral_flow.rs	New model implementation, schema registration, variant declaration, example-db spec, tests module hook-up
src/models/graph/mod.rs	Registers the new graph submodule, re-export, and adds example-db spec aggregation
src/models/mod.rs	Re-exports the new model from the top-level models module
src/lib.rs	Re-exports the model in the public prelude
src/unit_tests/models/graph/undirected_two_commodity_integral_flow.rs	New unit tests for creation/evaluation/serialization and overflow edge cases
src/unit_tests/trait_consistency.rs	Adds trait-consistency coverage for the new model
src/example_db/fixtures/examples.json	Adds canonical example fixture entry for the new model
src/example_db/model_builders.rs	Clarifies model-example sourcing (graph registry)
src/unit_tests/example_db.rs	Formatting tweak in fixture verification output/labeling
src/unit_tests/export.rs	Formatting tweak for JSON line assertion
problemreductions-cli/src/cli.rs	Adds --capacities and terminal/requirement flags + help text/examples for pred create
problemreductions-cli/src/commands/create.rs	Implements pred create UndirectedTwoCommodityIntegralFlow ... parsing/validation and adds type hints/example string
problemreductions-cli/src/problem_name.rs	Adds alias-resolution test coverage for the new canonical name
problemreductions-cli/tests/cli_tests.rs	Adds CLI tests for list, show, and create for the new model
docs/src/reductions/problem_schemas.json	Regenerated schema JSON including the new model entry
docs/src/reductions/reduction_graph.json	Regenerated reduction graph JSON including the new variant node
docs/paper/references.bib	Adds Even–Itai–Shamir (1976) reference
docs/paper/reductions.typ	Adds paper section + figure/example narrative for the new model

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[zazabap]

Final review passed — all CI green, coverage fixed, quality ~82%.

[zazabap]

Final review passed — conflicts resolved, all weaknesses fixed, quality ~82%.