Fix transition prescription consistency - #190

Summary

• validate complete transition context with one applicability law before reporting PRESCRIBED
• run side-effect-free effect preparation before prescription so deterministic apply refusals cannot appear late
• return CANDIDATE while required parameters are unbound, then require targeted re-resolution
• repair retained-goal, disabled-host, unstaged-recovery, and volatile-provider selection paths
• regenerate checked architecture projections and update generated host contracts

Verification

• python3 .github/scripts/release_notes.py validate
• python3 -m unittest discover -s .github/tests -p 'test_*.py'
• python3 .github/scripts/run_go_tests.py --jobs 10
• cd boatstack && go test -race ./...
• cd boatstack && go vet ./...
• cd boatstack && go build ./...
• git diff --check