fix(openrouter): use correct X-Title header for app attribution

OpenRouter requires 'X-Title' header for app attribution, not
'X-OpenRouter-Title'. The incorrect header name caused OpenRouter to not
recognize requests as coming from OpenClaw, resulting in free models
(e.g., xiaomi/mimo-v2-pro) being charged at full price.

Changes:
- Replace 'X-OpenRouter-Title' with 'X-Title' per OpenRouter docs
- Remove unnecessary 'X-OpenRouter-Categories' header
- Update tests to match corrected headers

Reference: https://openrouter.ai/docs/app-attribution
Fixes #50738

src/agents/provider-attribution.test.ts

@@ -34,8 +34,7 @@ describe("provider attribution", () => {
       version: "2026.3.14",
       headers: {
         "HTTP-Referer": "https://openclaw.ai",
-        "X-OpenRouter-Title": "OpenClaw",
-        "X-OpenRouter-Categories": "cli-agent",
+        "X-Title": "OpenClaw",
       },
     });
   });
@@ -47,8 +46,7 @@ describe("provider attribution", () => {
       }),
     ).toEqual({
       "HTTP-Referer": "https://openclaw.ai",
-      "X-OpenRouter-Title": "OpenClaw",
-      "X-OpenRouter-Categories": "cli-agent",
+      "X-Title": "OpenClaw",
     });
   });
 

src/agents/provider-attribution.ts

@@ -54,8 +54,7 @@ function buildOpenRouterAttributionPolicy(
     ...identity,
     headers: {
       "HTTP-Referer": "https://openclaw.ai",
-      "X-OpenRouter-Title": identity.product,
-      "X-OpenRouter-Categories": "cli-agent",
+      "X-Title": identity.product,
     },
   };
 }