The terminal's runs list cancels a queued or running crew run with `x` and a confirm, as the run page does #7230

For: the owner stops a crew run from the terminal without opening a browser. Today the page and MCP stop can cancel a run; the terminal cannot.

cancelRepoRun(app, actor, repo, runId) (src/actions/runs.ts:243) is reached from the web run page and MCP stop. src/tui/screens/runs.ts only filters (s) and refreshes (r).

Done:

• [ ] On a queued or running run the viewer may write to, the key hints show x cancel. It asks a one-line confirm that names the run. Yes calls cancelRepoRun, and the row's state becomes cancelled. No changes nothing.
• [ ] The key is not shown on a finished run, or to a reader. A run that finished meanwhile answers in one line, from the finished error.
• [ ] A new test/tui-run-cancel.test.ts drives the screen. It covers: confirm then cancelled, cancel then still running, the key absent on a finished run and for a reader.

Files: src/tui/screens/runs.ts, one test. Risk: low.