feat(a3): port build pipeline (vm new, build run, artifacts collect)

Implements Phase A3 of plans/implementation-plan-A-B.md:

- commands/vm.py: vm new (replaces New-BuildVM.ps1)

- commands/build.py: build run (replaces Invoke-RemoteBuild.ps1) with WinRM/SSH dispatch and stdout streaming for act_runner

- commands/artifacts.py: artifacts collect (replaces Get-BuildArtifacts.ps1) using transport.fetch()

- 3 PS scripts reduced to shims preserving \0

- Pester tests/{New-BuildVM,Wait-VMReady,Remove-BuildVM}.Tests.ps1 removed; equivalent cases covered in pytest

- Phase C hook: build/artifacts accept opaque VmHandle/vmx; no Windows path assumptions

Tests: 91 pytest, ruff clean, mypy --strict clean, coverage 78.27% (>=70 gate).

Master checklist + step A3 attivita + 'definizione di fatto' updated; A3-closeout.md added.

src/ci_orchestrator/__main__.py

@@ -1,8 +1,8 @@
 """CLI entry point.
 
 Phase A2 ships ``wait-ready``, ``vm`` (remove/cleanup), ``monitor``
-(disk/runner) and ``report`` (job). Subsequent phases add ``vm new``,
-``build``, ``artifacts``, ``job``.
+(disk/runner) and ``report`` (job). Phase A3 adds ``vm new``, ``build``,
+``artifacts``. Subsequent phases add ``job``.
 """
 
 from __future__ import annotations
@@ -12,6 +12,8 @@ import time as time
 import click
 
 from ci_orchestrator import __version__
+from ci_orchestrator.commands.artifacts import artifacts
+from ci_orchestrator.commands.build import build
 from ci_orchestrator.commands.monitor import monitor
 from ci_orchestrator.commands.report import report
 from ci_orchestrator.commands.vm import vm
@@ -34,6 +36,8 @@ def cli() -> None:
 
 cli.add_command(wait_ready)
 cli.add_command(vm)
+cli.add_command(build)
+cli.add_command(artifacts)
 cli.add_command(monitor)
 cli.add_command(report)