test(runtime): add cross-module integration tests (P1.2)
Add integration_tests.rs with 11 tests covering:
- stale_branch + policy_engine: stale detection flows into policy,
fresh branches don't trigger stale rules, end-to-end stale lane
merge-forward action
- green_contract + policy_engine: satisfied/unsatisfied contract
evaluation, green level comparison for merge decisions
- reconciliation + policy_engine: reconciled lanes match reconcile
condition, reconciled context has correct defaults, non-reconciled
lanes don't trigger reconcile rules
- stale_branch module: apply_policy generates correct actions for
rebase, merge-forward, warn-only, and fresh noop cases
These tests verify that adjacent modules actually connect correctly
— catching wiring gaps that unit tests miss.
Addresses ROADMAP P1.2: cross-module integration tests.
69b9232acf