feat: collaboration rooms with switchable presenter (#1328)

* feat: add collaboration rooms with switchable presenter

Rooms are a group of members watching one stage - the live SSH/RDP/VNC
session the current presenter shares. Any member can take over the
stage; the host can invite, force-stop and end the meeting. Stages
reuse session_shares (new room share type), so gating, recording,
expiry and the global sharing toggle all apply unchanged.

* feat: add stage control handoff to collaboration rooms

The presenter or host can grant any member write access to the live
stage and take it back; members can raise a hand to ask. SSH flips the
participant's permission on the live gate; RDP/VNC re-mint the viewer's
join token. Control clears on every stage switch.

* feat: guest links, role invites and invite awareness for collab rooms

- Anonymous guest link per room (host toggles/rotates), followed by
  polling the public resolve endpoint; SSH guests join over the terminal
  WS with roomGuestToken, guac guests get read-only join tokens
- Invite by role (expands to current members, snapshot semantics)
- Toast when a room you were invited to appears
- Stale stages are cleared lazily when the presenter is gone
- Telnet presenting, expired-tab fallback, documented single-instance
  and guac-kick limits
- Tests for the collab routes, room hub, share access and control flip

* fix: keep remote desktop collaboration read-only

src/ui/features/terminal/Terminal.tsx

@@ -131,6 +131,8 @@ interface SSHTerminalProps {
   onOpenTab?: (type: TabType) => void;
   /** False when this terminal sits in an unfocused split pane. */
   isFocusedPane?: boolean;
+  /** Fires when the backend reports the created session id (collab presenting). */
+  onSessionReady?: (sessionId: string) => void;
 }
 
 const ALTERNATE_SCREEN_SEQUENCE = /\x1b\[\?(47|1047|1049)([hl])/g;
@@ -154,6 +156,7 @@ const TerminalInner = forwardRef<TerminalHandle, SSHTerminalProps>(
     {
       hostConfig,
       isVisible,
+      onSessionReady,
       splitScreen = false,
       onClose,
       onTitleChange,
@@ -1936,6 +1939,7 @@ const TerminalInner = forwardRef<TerminalHandle, SSHTerminalProps>(
             }
           } else if (msg.type === "sessionCreated") {
             sessionIdRef.current = msg.sessionId;
+            onSessionReady?.(msg.sessionId);
             if (hostConfig.instanceId) {
               import("@/main-axios").then(({ patchOpenTab }) => {
                 patchOpenTab(hostConfig.instanceId!, {