An issue's page fits a 390 px phone: its title, body and conversation wrap instead of scrolling sideways #9345

The owner opens an issue's page on a 390 px phone. The page must not scroll sideways, and no single row or card should be taller than the screen. Follow the pattern of test/bets-card-fit.test.ts (#9286), as #9323–#9328 do for their pages.

Done looks like:

• [ ] A test renders an issue's page with seeded long content: a 300-character unbroken word, a long title, many rows. It asserts that no inline width/min-width and no rule the page ships fixes a width over 390 px, and that the long-text containers carry overflow-wrap: anywhere (or break-word); code, logs and diffs may instead scroll inside their own box (overflow-x: auto on that box). It fails without the fix, or, if the page already fits, it pins that.
• [ ] Anything it finds is fixed in src/web/studio/tell.ts. Any new class is named in docs/design/areas/tell.md (create it if absent), not docs/DESIGN.md.
• [ ] The pull description links the preview's phone look of /preview-admin/sample/issues/1, and says in one line whether it scrolls sideways.
• [ ] bun scripts/design-lint.ts passes. Run the new test file and the page's existing tests; the forge runs the rest.

Files: src/web/studio/tell.ts (tellPage), docs/design/areas/tell.md, one new test file. Risks: change no route and no data read. Don't touch src/http/api.ts. One page per pull; do not widen it to sibling pages.

Replaced by #9384. Box 3 asked for a link to the preview's phone look of /preview-admin/sample/issues/1, but a look taken as the owner is the writers' picture (#727), so the crew only ever sees its thumb and the box could not be met. #9384 keeps boxes 1, 2 and 4 and asks for the verdict from the forge check's own 390×844 measurement instead. #9386 makes that measurement readable from the pull's looks.