Build the owner-facing multiplayer room product

[danielblignaut]

What to build

Build the owner-facing multiplayer room product on top of the merged ChatKit room and invitation contracts. Owners should be able to see the roster and roles, invite canonical users, review pending invitations, revoke invitations, and remove participants without introducing frontend-specific authorization rules.

Use shared client-runtime contracts and shared UI for web and Electron. Preserve the existing backend rule that room roles never widen session visibility or ownership.

Acceptance criteria

• Web and Electron expose the same room roster, participant roles, presence/typing state, invitation state, and owner actions.
• Invite, accept/decline, revoke, leave, and remove actions use the generated ChatKit APIs through shared client-runtime contracts.
• Pending invitees see only their invitation, never room history or attachments before acceptance.
• Participant removal updates visible state and revokes session-bound capabilities without requiring reload.
• The UI renders server-authored role/status descriptors and contains no provider-specific authorization branches.
• Focused component/runtime tests and a real browser workflow cover invite-to-acceptance and revocation.

Blocked by

None - can start immediately; API PR #227 is merged.