fix(sim-core): stabilize labor runtime clearing and phase orchestration

[JoeHowarth]

Summary

• refactor world tick orchestration to execute labor/production/market/mortality phase-wide across settlements, eliminating settlement-order coupling
• fix labor runtime correctness by deriving labor skills from runtime state, using recipe-output-specific MVP pricing, and enforcing owner-level budget reservation before committing assignments
• add regression coverage for all four runtime issues plus a multi-tick shared-merchant order-invariance test, and record the key learnings in sim-core/LEARNINGS.md

Validation

• cargo fmt
• cargo clippy --fix --all-targets --all-features --allow-dirty --allow-staged
• cargo clippy -q --all-targets --all-features
• cargo test -q