feat(web): workbench room is the child tenant's mail thread; legacy chat client deleted (CL-8435)

A workbench is a child tenant, so /w/:tenantId now renders that tenant's
mailbox: participants are its principals, the timeline is its mail
threads with native in-reply-to chains as sub-threads, and a message is
addressed to every agent in the room through one send seam. Creating a
workbench is a stock tenant create plus a stock member invite per agent,
Myra always included.

The chat client for the deleted /chat/workbenches routes is gone, along
with every module that only existed to serve it.

Author: TheGreatAxios

apps/web/src/agent-chat-launch.test.ts

@@ -460,3 +460,18 @@ export function useAgentDirectory(tenantId: string | undefined): APIQuery<AgentD
   });
   return toAPIQuery(result);
 }
+
+// The guided capability-add surface: only what this tenant actually has.
+const CapabilityInventoryWire = type({
+  toolPackages: type({ name: "string" }).array(),
+  skills: type({ name: "string" }).array(),
+  models: type({ canonicalName: "string" }).array(),
+});
+export type CapabilityInventory = typeof CapabilityInventoryWire.infer;
+
+export function listCapabilityInventory(tenantId: string): Promise<CapabilityInventory> {
+  return getJSON(
+    `/api/tenants/${tenantId}/agent-definitions/capabilities/inventory`,
+    CapabilityInventoryWire,
+  );
+}

apps/web/src/agent-chat-launch.ts

@@ -3860,3 +3860,58 @@ button.mission-control-jump-row:hover {
 .chat-composer > textarea {
   width: 100%;
 }
+
+/* A workbench room: timeline in the stage, sub-thread replies beside it. */
+.room-layout {
+  display: flex;
+  min-height: 0;
+  flex: 1;
+}
+.room-participants {
+  display: flex;
+  flex-wrap: wrap;
+  gap: 0.5rem;
+  margin: 0 0 1rem;
+  padding: 0;
+  list-style: none;
+  font-size: 0.82rem;
+  color: var(--muted-foreground);
+}
+.room-participants > li {
+  display: flex;
+  align-items: center;
+  gap: 0.35rem;
+}
+.room-replies-link {
+  display: block;
+  margin-top: 0.35rem;
+  padding: 0;
+  border: 0;
+  background: none;
+  font-size: 0.78rem;
+  color: var(--muted-foreground);
+  cursor: pointer;
+}
+.room-replies-link:hover {
+  color: var(--foreground);
+}
+.room-subthread {
+  display: flex;
+  flex-direction: column;
+  width: 22rem;
+  min-height: 0;
+  overflow-y: auto;
+  padding: 1rem;
+  border-left: 1px solid var(--border);
+}
+.room-subthread-head {
+  display: flex;
+  align-items: center;
+  justify-content: space-between;
+  margin-bottom: 0.75rem;
+}
+.room-subthread-head > h2 {
+  margin: 0;
+  font-size: 0.95rem;
+  font-weight: 600;
+}

apps/web/src/agent-dm-launch.test.ts

@@ -12,6 +12,15 @@ export const chatKeys = {
   childTenants: (tenantId: string) => ["tenant", tenantId, "child-tenants"] as const,
 };
 
+/** One key factory per room (a workbench child tenant), so a send
+ * invalidates the room's timeline and roster together. */
+export const roomKeys = {
+  scope: (tenantId: string) => ["room", tenantId] as const,
+  tenant: (tenantId: string) => ["room", tenantId, "tenant"] as const,
+  participants: (tenantId: string) => ["room", tenantId, "participants"] as const,
+  timeline: (tenantId: string) => ["room", tenantId, "timeline"] as const,
+};
+
 export const CHATS_PATH_PREFIX = "/chats";
 export const NEW_CHAT_PATH = `${CHATS_PATH_PREFIX}/new`;