refactor: schema-driven pred create (11K → 2.3K lines)

[GiggleLiu]

Summary

• Replace the 11,049-line create.rs with schema-driven generic dispatch using existing registry factory functions
• New create.rs is 2,295 lines (79% reduction), split into 4 files totaling 8,820 lines
• CLI creation now auto-maps ProblemSchemaEntry fields to CLI flags via snake_case → kebab-case convention
• New models need only matching CLI flags + type parser support — no match arm in create.rs
• All existing CLI flags preserved via #[arg(alias)] for backward compatibility
• Updated add-model skill, review-structural skill, and CLAUDE.md to reflect new conventions

Architecture

ProblemSchemaEntry fields → flag_map() → parse_field_value() → JSON → factory() → DynProblem

File structure after refactor

File	Lines	Purpose
create.rs	2,295	Main dispatch, help, random, example paths
create/schema_support.rs	2,519	Type parsers, flag mapping, generic resolution
create/schema_semantics.rs	1,308	Per-problem validators, derived values
create/tests.rs	2,698	Schema-driven path tests

What's preserved

• All pred create commands work identically
• --random and --example paths unchanged
• Old flag names work via aliases
• Constructor/try_from validation still catches invalid input

Known trade-offs

• Error messages are more generic (schema-driven vs hand-crafted usage strings)
• Cross-field validation now happens at factory level (still fails, just later)

Test plan

• cargo test -p problemreductions-cli passes
• cargo clippy --workspace --all-targets -- -D warnings clean
• make check passes
• make cli-demo (exercises all commands end-to-end)
• Manual smoke test: pred create MIS --graph 0-1,1-2, pred create SAT --num-vars 3 --clauses "1,2;-1,3", pred create BinPacking --sizes 3,3,2 --capacity 5

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.17%. Comparing base (c57a131) to head (0701d41).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1008      +/-   ##
==========================================
+ Coverage   98.15%   98.17%   +0.01%     
==========================================
  Files         896      896              
  Lines       91150    91715     +565     
==========================================
+ Hits        89472    90039     +567     
+ Misses       1678     1676       -2     

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