Mobile web (claude.ai): long-press opens the message menu instead of selecting text — no way to copy a partial selection

On claude.ai in mobile Safari (iOS), long-pressing inside an assistant
message opens the message action sheet (Copy message / Copy message as
Markdown / Attach message as context / Pin as chapter). It never places a
text cursor, so partial text selection is impossible — the only copy
granularity available on mobile is the whole message.

On desktop this is annoying but survivable because Cmd+C / Ctrl+C still
copies the selection. On mobile there is no keyboard path, so there is no
workaround inside the app at all. The only way I've found to copy a
paragraph out of a reply is Safari Reader mode or "Request Desktop Site",
both of which leave the app.

Repro (iPhone / iOS Safari):
1. Open any conversation at claude.ai
2. Long-press on a few words inside an assistant message
3. The action sheet appears; no selection handles, no cursor

Expected: long-press selects text (native behaviour), or the sheet
includes a "Copy selection" action.

Related, all closed: #61484 (closed by the stale bot, not resolved),
#66131, #64674, #50386, #53975, #50425, #59228, #23018. Every one of them
is desktop right-click; the mobile web case isn't covered by any of them,
which is why I'm opening a new one as the bot on #61484 suggested.