feat: simplify CLI runtime state and startup behavior

[jBernavaPrah]

Summary

• publish one validated .phoxal/run/robot runtime root for both run and simulation, while keeping ~/.phoxal/run/simulator.lock as the cross-project Webots lock
• remove the file-backed supervisor snapshot/action protocol and the cache command; status is now bus-backed and project cleanup is an explicit idle-only .phoxal reset
• make artifact updates version-and-digest correct, transactionally refresh all packages, preserve prior artifacts on failure, stay read-only in dry-run, and prune inactive versions after activation
• gate both managed and externally reused routers on a CLI-owned bus connection before starting downstream participants

Why

The CLI had several overlapping sources of runtime truth: source-tree staging, supervisor JSON files, cache maintenance commands, and artifact versions that could remain stale after a digest changed. This consolidates launch state under one project-local runtime root and keeps live readiness in the supervising CLI process.

Closes phoxal/organization#903

Validation

• cargo test --workspace
• cargo check --workspace
• cargo clippy --workspace --all-targets -- -D warnings
• cargo fmt --all -- --check
• git diff --check
• clean-room update followed by check --strict
• clean-room live Webots startup verified router, tools, Webots, simulator, and service ordering without the previous initial connection warnings or restart flap; the later safety-service failure was traced to current robot-v1 schema being ahead of the released CLI dependency and is outside this issue

Review notes

• intentionally no backward-compatible cache, file-backed status, supervisor-state, or supervisor-actions paths
• intentionally no separate follow-up issues; the agreed scope is contained here