Build create arguments lazily from problem schemas

[isPANN]

Summary

• replace the monolithic derived CreateArgs with a schema-driven parser that expands flags only for the selected problem
• model construction inputs explicitly as external, derived, or composite and share that semantic definition between CLI generation and object construction
• remove obsolete aliases and the enlarged-thread-stack workaround; keep completion generation shallow
• avoid repeated registry/schema scans and derive numeric parsers from each concrete schema type

Stack

This PR is stacked on #1083 and intentionally targets 1075-growth-domain.

Verification

• cargo clippy -p problemreductions-cli --all-targets -- -D warnings
• cargo test -p problemreductions-cli
• cargo test --workspace --quiet
• git diff --check