refactor(search): fold zai-search into the glm provider

The separate zai-search entry showed "No connections" on the web search
page because credentials live on the `glm` connection, not on it. Every
other provider that does both chat and search (antigravity, kimi, xai,
gemini) declares webSearch on the provider itself, so do the same here.

- glm gains serviceKinds ["llm", "webSearch"] and the MCP searchConfig
- the request builder / normalizer move from "zai-search" to "glm"
- drop the zai-search registry entry and its svg logo, which also
  removes the only need for svg logo support in getProviderIconSrc

ollama-search keeps its own entry and credentialFallback: its search
endpoint is unrelated to the ollama chat transport.

open-sse/providers/registry/index.js

@@ -98,7 +98,6 @@ import p95 from "./xai.js";
 import p96 from "./xiaomi-mimo.js";
 import p97 from "./xiaomi-tokenplan.js";
 import p98 from "./youcom.js";
-import p124 from "./zai-search.js";
 import p99 from "./alims-intl.js";
 import p100 from "./codebuddy-intl.js";
 // Temporarily hidden — no tool calling support (trae SOLO agent / windsurf gRPC skip ToolCallChunk).
@@ -225,7 +224,6 @@ export default [
   p96,
   p97,
   p98,
-  p124,
   p99,
   p100,
   // p102, // trae — hidden, no tool calling