The terminal's System screen says how the forge is: the version and commit it runs, draining or not, the rollout and its incidents, as MCP `health` does #7296

For: the owner who wants to know, in calm words, whether the forge is well before deciding anything. Trust and calm means the answer is one look away and quiet when all is well.

readHealth (src/actions/health.ts) is reached from MCP health. The terminal's System screen (src/tui/screens/system.ts) shows the machine but not the forge's own state.

Done:

• [ ] The System screen's first line: version, short commit, and "serving" or "draining".
• [ ] When a rollout is in progress or has incidents, one more line says it in words; when there are none, nothing more is drawn (no green noise).
• [ ] It reads readHealth, the same view MCP returns; who may see it is the same as MCP.
• [ ] A test in test/tui-system*.test.ts or a new one: the line shows the version and commit; a seeded incident adds one line; none adds nothing.

Files: src/tui/screens/system.ts, one test. Risk: low; read only.