Feature: Pinned messages #73

Goal

Let room members pin important messages and browse them from the room header, similar to Element and Discord.

Scope

• Read and display pinned messages for the active room
• Open a pinned-messages panel from the room header toolbar
• Pin and unpin messages from the message action bar when room power levels allow it
• Jump from a pinned entry to the message in the main timeline
• English and German UI strings
• Replace the current disabled pin placeholder in ChatRoomHeaderToolbar

Out of scope for this issue:

• Premium-only features
• Pinned message search or filters beyond a simple chronological list

Branch

feature/pinned-messages

Acceptance Criteria

• The room header pin control opens a pinned-messages panel in the right sidebar
• Pinned messages are listed with sender, snippet, and pin time
• Users with sufficient power level can pin and unpin messages from the message action bar
• Selecting a pinned message focuses or scrolls to that message in the room timeline
• Pin and unpin changes sync from the homeserver and update the list without reload
• The panel shows an empty state when the room has no pinned messages
• The panel works alongside the existing threads and members sidebar modes

Test Checklist

Unit

• Pinned event/state parsing and timeline mapping
• Pin and unpin client helpers respect room power levels

Integration

• Header toolbar switches the right sidebar to the pinned panel
• Pin and unpin updates the visible pinned list for the active room

E2E

• Pin a message, reopen the room, and verify it appears in the pinned list
• Open a pinned entry and verify navigation to the original message
• Unpin a message and verify it disappears from the pinned list

Notes

• Shipped: matrixRoomPinnedEvents, matrixPinnedMessageEntries, ChatPinnedMessagesPanel, header toolbar + action bar pin/unpin, jumpToMessageInRoom with timeline pagination, EN/DE i18n, unit/component/E2E coverage.
• Pin time in the list uses the pinned message's timestamp (not per-pin state history).
• Follow the existing room header toolbar and right-sidebar patterns used for threads and members.
• Matrix room state m.room.pinned_events is the expected protocol baseline; align with Element behavior where practical.