Two-machine manifest, bootstrap, and reconcile smoke

[BramVR]

Parent: #70

What to build

Add a two-machine smoke for the actual CodeMesh control-plane loop: machine identity, manifest entry files, bootstrap, hydration, and reconcile drift.

Use two isolated CodeMesh homes on the same host as the default fixture. Optionally allow a live GitHub manifest remote once the live lane is ready.

Acceptance criteria

• The smoke creates Machine A and Machine B with separate CODEMESH_HOME, HOME, git config, machine ids, and workspace roots.
• Machine A registers a project and writes the expected manifest entry state.
• Machine B bootstraps from the manifest without cloning unrelated projects by default.
• Machine B hydrates one selected project and records provenance for remote, base, desired path, and machine id.
• Reconcile detects at least one deliberate drift case and prints a dry-run plan before any mutation.
• The case proves no source checkout from Machine A is reused by Machine B.
• The report includes both machine ids, manifest location, hydrated project id, drift summary, and cleanup status.

Blocked by

• Live e2e harness guardrails and report mode #88
• Machine Registry and machine register #80
• Workspace Manifest per-project entries #81
• Reconciliation drift plan #82
• Bootstrap topology without cloning #83

Cost guardrail

• Must stay free by default: two-machine smoke uses two isolated local CodeMesh homes on one host. Any live manifest remote uses public GitHub over HTTPS and SKIPs on unavailable free prerequisites.