Add a Mentions room list filter (#5885)

* Add a Mentions room list filter

Adds a new filter chip to the room list that shows only rooms with
unread mentions, using the new mentions room list filter from the
Rust SDK (matrix-org/matrix-rust-sdk branch matthew/mentions-filter).

The SDK version needs bumping to a release that includes the new
filter kind before this can build against the released components.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

* Order the room list filters by expected usage

Move Favourites ahead of People and Rooms so the more commonly used
filters (Unreads, Mentions, Favourites) sit first in the chip row —
Rooms and Invites are used rarely enough that it's fine for them to
wrap off the side.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Uk8aPxHn3BHCe52L226jdG

* update the SDK and use the appropriate rust filter types

* preview tests + app settings flag for mentions

---------

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
Co-authored-by: Mauro Romito <mauro.romito@element.io>

UnitTests/Sources/RoomListFiltersStateTests.swift

@@ -13,7 +13,8 @@ import Testing
 final class RoomListFiltersStateTests {
     var appSettings: AppSettings
     var state: RoomListFiltersState
-    let allCasesWithoutLowPriority = RoomListFilter.allCases.filter { $0 != .lowPriority }
+    /// The filters that aren't hidden behind a feature flag.
+    let defaultFilters = RoomListFilter.allCases.filter { $0 != .mentions && $0 != .lowPriority }
     
     init() {
         appSettings = AppSettings.volatile()
@@ -24,7 +25,7 @@ final class RoomListFiltersStateTests {
     func initialState() {
         #expect(!state.isFiltering)
         #expect(state.activeFilters == [])
-        #expect(state.availableFilters == allCasesWithoutLowPriority)
+        #expect(state.availableFilters == defaultFilters)
     }
     
     @Test
@@ -32,11 +33,11 @@ final class RoomListFiltersStateTests {
         state.activateFilter(.unreads)
         #expect(state.isFiltering)
         #expect(state.activeFilters == [.unreads])
-        #expect(state.availableFilters == [.people, .rooms, .favourites])
+        #expect(state.availableFilters == [.favourites, .people, .rooms])
         state.deactivateFilter(.unreads)
         #expect(!state.isFiltering)
         #expect(state.activeFilters == [])
-        #expect(state.availableFilters == allCasesWithoutLowPriority)
+        #expect(state.availableFilters == defaultFilters)
     }
     
     @Test
@@ -49,7 +50,7 @@ final class RoomListFiltersStateTests {
         state.deactivateFilter(.people)
         #expect(!state.isFiltering)
         #expect(state.activeFilters == [])
-        #expect(state.availableFilters == allCasesWithoutLowPriority)
+        #expect(state.availableFilters == defaultFilters)
         
         state.activateFilter(.rooms)
         #expect(state.isFiltering)
@@ -87,7 +88,7 @@ final class RoomListFiltersStateTests {
         state.clearFilters()
         #expect(!state.isFiltering)
         #expect(state.activeFilters == [])
-        #expect(state.availableFilters == allCasesWithoutLowPriority)
+        #expect(state.availableFilters == defaultFilters)
     }
     
     @Test
@@ -98,7 +99,7 @@ final class RoomListFiltersStateTests {
         
         state.deactivateFilter(.favourites)
         #expect(state.activeFilters == [])
-        #expect(state.availableFilters == allCasesWithoutLowPriority)
+        #expect(state.availableFilters == defaultFilters)
         
         state.activateFilter(.rooms)
         #expect(state.activeFilters == [.rooms])
@@ -121,17 +122,38 @@ final class RoomListFiltersStateTests {
         enableLowPriorityFeature()
         #expect(!state.isFiltering)
         #expect(state.activeFilters == [])
-        #expect(state.availableFilters == RoomListFilter.allCases)
+        #expect(state.availableFilters == defaultFilters + [.lowPriority])
         
         state.activateFilter(.lowPriority)
         #expect(state.activeFilters == [.lowPriority])
         #expect(state.availableFilters == [.unreads, .people, .rooms])
     }
     
+    // MARK: Mentions feature flag
+    
+    /// Don't forget to add .mentions into the mix above when enabling the feature.
+    @Test
+    func withMentionsFeature() {
+        enableMentionsFeature()
+        #expect(!state.isFiltering)
+        #expect(state.activeFilters == [])
+        #expect(state.availableFilters == [.unreads, .mentions, .favourites, .people, .rooms, .invites])
+        
+        state.activateFilter(.mentions)
+        #expect(state.isFiltering)
+        #expect(state.activeFilters == [.mentions])
+        #expect(state.availableFilters == [.unreads, .favourites, .people, .rooms])
+    }
+    
     // MARK: - Helpers
     
     private func enableLowPriorityFeature() {
         appSettings.lowPriorityFilterEnabled = true
         state = RoomListFiltersState(appSettings: appSettings)
     }
+    
+    private func enableMentionsFeature() {
+        appSettings.mentionsFilterEnabled = true
+        state = RoomListFiltersState(appSettings: appSettings)
+    }
 }