iOS: Group by Project setting for the Sessions page

[wing-anara]

Summary

• Adds a Group by Project setting on iOS. When on, sessions outside Pinned and your sections are grouped by project instead of listed under "Recent". This works like the desktop sidebar's "By project": clones and worktrees of one repository share a group named after the main checkout, and sessions with no project are grouped per device as "Home · ". Groups are ordered by their most recent session.
• The toggle is in Settings → Sessions and in the Sessions page's ⋯ menu. The menu item is rebuilt each time it opens, so it always matches the setting. The setting is stored on the phone only, like the desktop's sidebar setting.
• Project groups fold like the other sections and remember their fold state, and Collapse All folds them too.

Screenshots (demo workspace)

Off	Setting	On

Test plan

• Simulator build (iPhone 17 Pro)
• Demo workspace on iPhone and iPad: "Recent 4" becomes groups for zeron, Home · MacBook Pro, edge and blog
• Temporary UI test scrolled to the Settings toggle, switched it on, and checked the Sessions page regrouped live (screenshots above)

🤖 Generated with Claude Code

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[wingleeio]

Resubmitting from wingleeio.