Make deployment output prefixing and phase colors consistent

[omry]

Problem

Deployment-aware output is currently inconsistent:

• install progress such as "installing deployment... done" is unprefixed
• install-result lines use the long [DEPLOYED : arbiter] prefix but are not phase-colored
• health and status use a phase-colored [DEPLOYED : arbiter] prefix
• workload log lines are streamed without a deployment prefix
• child-process or systemd output emitted through Reploy may be unprefixed

This makes it hard to distinguish Reploy output, workload output, and unrelated caller output in a combined terminal or captured log.

Proposed convention

Once Reploy has resolved the environment identity, use a compact per-line prefix:

[arbiter]

Use the phase color for the entire line: the existing staging color for staged output and the existing deployed color for installed output.

At the start of a deployment-aware output stream, print a self-describing line in that phase color:

[arbiter] Staging output uses this color.
[arbiter] Deployed output uses this color.

Then consistently apply the same prefix and phase color to Reploy progress/results, workload logs, and child/systemd output that Reploy emits.

Requirements

• Audit deployment-aware output paths rather than fixing only logs.
• Keep the [arbiter] prefix in NO_COLOR and redirected output.
• Keep the initial line textual so the phase remains identifiable without color.
• Preserve workload-provided ANSI formatting rather than corrupting it.
• Do not attempt to prefix output from systemctl or another command invoked directly by an external script; only output routed through Reploy is in scope.