feat(tavily): add X-Client-Source attribution header

Add optional extraHeaders param to postTrustedWebToolsJson and use it
to send X-Client-Source: openclaw on all Tavily API requests (search
and extract), matching the Tavily Python SDK's client_source mechanism.

extensions/tavily/src/tavily-client.ts

@@ -119,6 +119,7 @@ export async function runTavilySearch(
       apiKey,
       body,
       errorLabel: "Tavily Search",
+      extraHeaders: { "X-Client-Source": "openclaw" },
     },
     async (response) => (await response.json()) as Record<string, unknown>,
   );
@@ -200,6 +201,7 @@ export async function runTavilyExtract(
       apiKey,
       body,
       errorLabel: "Tavily Extract",
+      extraHeaders: { "X-Client-Source": "openclaw" },
     },
     async (response) => (await response.json()) as Record<string, unknown>,
   );

src/agents/tools/web-search-provider-common.ts

@@ -100,6 +100,7 @@ export async function postTrustedWebToolsJson<T>(
     body: Record<string, unknown>;
     errorLabel: string;
     maxErrorBytes?: number;
+    extraHeaders?: Record<string, string>;
   },
   parseResponse: (response: Response) => Promise<T>,
 ): Promise<T> {
@@ -110,6 +111,7 @@ export async function postTrustedWebToolsJson<T>(
       init: {
         method: "POST",
         headers: {
+          ...params.extraHeaders,
           Accept: "application/json",
           Authorization: `Bearer ${params.apiKey}`,
           "Content-Type": "application/json",