Fix sync startup regressions and add cp progress

[acmore]

Summary

• add transient progress reporting for cp operations and supporting kube progress hooks
• fix syncthing session cleanup, early readiness signaling, and session-safe local listen addresses
• bound mesh health probing and document the status details behavior

Testing

• env GOCACHE=/tmp/go-build go test ./internal/cli ./internal/kube
• .venv/bin/pre-commit run --all-files --hook-stage manual okdev-gofmt

[acmore]

Superseded by the split PRs:

• Add cp transfer progress reporting #91 Add cp transfer progress reporting
• Fix syncthing startup and status regressions #92 Fix syncthing startup and status regressions