The terminal's pull screen takes back a shipped pull with one key and a confirm, as the page does #7212

For: the owner in the terminal can undo what shipped without opening a browser.

Today src/tui/screens/pull.ts ships and closes, but has no take-back. Only the web form reaches revertPull.

Done:

• [ ] On a merged pull the viewer may write to, the key hints show a take-back key, for example T. Pressing it asks a one-line confirm that names the pull. Yes calls revertPull (src/actions/revert.ts) and opens the new pull's screen. No changes nothing.
• [ ] The key is not shown on an open pull, on a mirror, or to an agent. Refusals read in the same words as the page.
• [ ] A new test/tui-take-back.test.ts drives the screen. It covers: the key absent on an open pull, confirm then the new pull, cancel then nothing made, and a second take-back refused as already taken back.

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