[#1268] Opt-in entry: connect the editor to the hub over Remote-SSH #1271

Acceptance Criteria

• A command connects the editor to the hub host via Remote-SSH using coordinates resolved from the projection.
• Missing/invalid hub coordinates produce an honest, actionable message — no crash, no half-opened window.

Testing Decisions

Extend the fleet-command / projection-reader suites with a coordinate-resolution case and a missing-config case (asserts the honest message). Extends #1268-S1's attach surface.

Key Decisions

• Coordinates come from the projection (one topology reader, ADR 0023) — never a hand-built host string or a second config source.

Constraints & Invariants

• One topology reader preserved.

Prior Art

• The projection reader; the fleet command surface; Remote-SSH as a first-class fleet posture (opt-in) — host-native tooling on the durable hub #1268-S1's attach path.

Source

• Part of Remote-SSH as a first-class fleet posture (opt-in) — host-native tooling on the durable hub #1268 · ADR 0025 · Blocked by Remote-SSH as a first-class fleet posture (opt-in) — host-native tooling on the durable hub #1268-S1.