Refresh README for current workflow model

[ArchonVII]

Summary

The README is stale and still reflects older agent/persona framing. Refresh it comprehensively so it describes the current reusable workflow provider model and explicitly removes the retired admiral/lieutenant/persona-agent workflow framing.

Acceptance Criteria

• README describes the current purpose of this repository as reusable GitHub Actions workflows and policy helpers.
• README no longer presents admiral/lieutenant/etc. persona agents as the operating model.
• README includes current workflow inventory, consumption pattern, verification guidance, and local development guidance.
• No workflow behavior changes are included.

Source

Requested by user in Codex session on 2026-06-11.