An admin sets the repository's description from the terminal's About card with `w`, as Settings does #8066

Intent: the owner fixes a repository's one-line description where they are reading it, without leaving the terminal for Settings.

Done looks like:

• [ ] The About card (src/tui/screens/about.ts) offers w "write description" only to a person who administers the repository (the same may() gate as a archive); an agent or a reader is not offered the key, and a press from them changes nothing.
• [ ] w opens a one-line prompt prefilled with the current description; enter saves through updateRepoSettings(app, actor, repo, { description }) in src/actions/repos.ts — the same path Settings and MCP repo_settings use, so the change is audited the same way; esc leaves it as it was.
• [ ] The description is validated as Settings validates it (same length cap, trimmed, control characters refused); a refusal is a toast in Settings' words, and the card is unchanged.
• [ ] After saving, the card redraws with the new description and a success toast; an empty description shows "No description." as today.
• [ ] A test in test/tui-about-description.test.ts drives the screen: an admin's w + text + enter changes the row and the audit trail; a non-admin has no w binding; esc changes nothing. It fails without the change.
• [ ] test/tui-about-golden.test.ts updated only for the new key hint, if the hint row shows it.

Files: src/tui/screens/about.ts, test/tui-about-description.test.ts, test/tui-about-golden.test.ts

Risks: w must not collide with an existing About binding (today y v a d t u f x e c p esc, and V in #8008); if it does, pick a free key and say so. Do not add a second write path — reuse updateRepoSettings. Does not touch docs/MCP.md, README.md or src/http/server.ts.

Brief: a builder who knows the tui screens (scout or mason).

Parked by the crew: the check stayed red through 2 automatic tries: a 40-file pull's second Files request is a diff cache hit and renders far less than the first (pull #8135 closed). Planner: split this smaller, or rewrite what done looks like; a person can also say what to try.