refactor(tools): drop serviceEndpoint from fabric-guild-list response

Pairs with Fabric.Backend.Center@9e1909a which removed the
serviceEndpoint column. The agent-driven recruitment model no longer
needs a service-to-service URL distinction — agents post recruitment
broadcasts directly via fabric-send-message using their normal
session, no backend dials Fabric anymore.

Removed:
  - FabricSession.guilds.serviceEndpoint type field
  - fabric-guild-list response mapping for serviceEndpoint
  - Tool description text that taught agents to plumb it into
    dialectic_propose_topic.announce_guild_base_url (that param is
    also gone — see Dialectic.OpenclawPlugin@3ce5439).

Kept:
  - guild.purpose field (intent-based discovery, still wanted)
  - guild.endpoint field (clients dial it directly; unchanged)

src/fabric-client.ts

@@ -10,13 +10,6 @@ export type FabricSession = {
     nodeId: string;
     name: string;
     endpoint: string;
-    // Service-to-service endpoint (e.g. http://backend-guild:7002) — what
-    // an in-deployment backend uses to reach this guild. Distinct from
-    // `endpoint` which is the client/browser-facing URL. Plumb this into
-    // `announce_guild_base_url` on dialectic_propose_topic so the
-    // dialectic-backend can actually dial it. Null when the admin hasn't
-    // configured it.
-    serviceEndpoint?: string | null;
     status: string;
     // free-form description of this guild's role; admin-set on Center.
     // null when the admin hasn't filled it in yet.