The terminal's changelog narrows releases by a word with `/`, and Enter on a release lists every pull it carried #7350

Intent: "when did that land?" is answered in the terminal in one search.

Done:

• [ ] On the changelog screen (src/tui/screens/changelog.ts), / takes a word and keeps only releases whose version or carried pull titles contain it (case-insensitive); esc clears it; the header says how many match.
• [ ] Enter on a release lists its pulls (#N title), and Enter on a pull opens it as today's Enter does.
• [ ] The read stays the one forgeChangelog call; a guest sees the same as today.
• [ ] A test (e.g. test/tui-changelog-find.test.ts) narrows to one release by a pull's word and opens its pull list.

Files: src/tui/screens/changelog.ts, a new test.