0.2.0

• buildvm ship and a per-project .buildvm file: every platform of an app in one command.
• Persistent per-app, per-platform DerivedData (incremental second builds) keyed by a stable
  project name instead of the staging directory's name; --name, --clean.
• Guest disk management: automatic pruning below a free-space floor, artifacts removed after a
  successful upload, buildvm clean.
• Host-side build lock so concurrent runs queue instead of corrupting one another.
• Preflight: expired / non-App-Store profiles, certificates the guest does not hold, git trees
  behind their upstream, already-uploaded build numbers, a beta Xcode in the guest.
• Failures print the compile/sign errors and keep the full log under ~/.local/state/buildvm/logs.
• altool retries transient failures; the Delivery UUID is captured.
• buildvm doctor, status --json, history, --version; a build ledger; a final
  machine-readable RESULT {json} line and per-phase timings.
• SSH keepalives for long archives; --exclude; --down.
• Fixed: status always reported one valid identity.
• Fixed: after buildvm down the next command never booted the VM and timed out (tart ip keeps
  answering with the last lease, so "has an IP" was mistaken for "is running").
• test/run.sh: hermetic tests for the logic that does not need the VM.