Feature: hide chat folder tabs

[mvsrcdst]

Summary

Adds the ability to hide individual chat folder tabs from the tab strip for folders you keep around but rarely check, so they stop cluttering the tab bar while the chats inside them stay fully intact (not archived, not muted, not touched) and reachable.

Comes with a full UI around it: hide a folder from its own tab's long-press menu, hide/show it from the Edit Folders settings screen (swipe action), reach all hidden folders via a long-press on the Chats tab bar icon, and once you're actually inside a hidden folder its tab pill temporarily reappears so you're not lost.

Purely a tab-bar visibility filter. No chat data, notifications, unread counts, folder membership, or archive state are touched - a hidden folder's chats behave exactly as before, they just don't have a tab.

Local-only: hiding a folder on one device does not hide it on your other logged-in devices/clients.

Behaviours:

• Viewing a hidden folder shows its tab pill again until you leave
• Folder tab long-press: Hide/Show toggle
• Hiding your current folder auto-jumps you to the first visible tab
• Chats tab-bar long-press: new "Hidden Folders" entry, unread badge, drill-down list
• All Chats row in that menu: real icon instead of blank
• Last visible folder (All Chats hidden) keeps its tab instead of going full-screen, hiding it too falls back to plain All Chats

Screenshots

Chats tab-bar long-press menu "Hidden Folders" row positioned right after "All Chats", before the visible folder list, and the "All Chats" row showing its new icon

No hidden folders -> no "Hidden Folders" menu by Chats tab-bar long-press

"Hidden Folders" expanded list of hidden folders each with its own badge, plus "Back"

A visible folder tab's long-press menu "Hide Folder"

The same folder now hidden and currently active, its tab pill temporarily visible in the strip, long-press shows "Show Folder"

Edit Folders menu: label for hidden folder

Edit Folders menu: swipe for Show/Hide a folder

Testing

• Tested on iOS Simulator 18.6/26.5
• Last visible folder keeps its tab when All Chats + all others hidden
• Hide "All Chats" + hide the only other folder (leaving nothing else) -> tab strip falls back to a plain "All Chats" list with no tab bar (last-resort safety net, no crash)
• Hide "All Chats" + hide a folder while other visible folders remain -> restart app -> opens to the first visible folder, not "All Chats"
• Hide the currently-selected first folder tab -> no crash
• Scroll to top, tap the Chats tab-bar icon repeatedly (jump-to-first-tab) -> never lands on a hidden folder
• Press "Hidden Folders" (bottom Chats tab-bar long-press menu) -> tap a hidden folder -> its tab pill appears in the strip, content matches
• Switch to another tab -> the hidden folder's tab pill disappears from the strip immediately
• While on a hidden folder, long-press its tab -> menu shows "Show Folder" -> tap -> folder now visible, badge in Hidden Folders menu drops accordingly
• Long-press a visible folder tab -> "Hide Folder" -> tap -> tab disappears immediately
• While standing on a hidden folder -> long-tap -> Show Folder -> long-tap -> hide it again -> immediately navigated to another visible tab, not stuck
• Chats tab-bar long-press menu -> "Hidden Folders" entry shows correct aggregate unread badge, hidden when no folders are hidden
• Notification for a chat in a hidden folder still fires and opens the chat normally
• Chats tab-bar long-press menu -> "All Chats" row shows the chat-bubbles icon, not blank