fix(openclaw): keep the User-Agent switch in sync with JSON header edits

The Send User-Agent switch was only derived from settingsConfig.headers
on mount and on preset reset. Editing headers directly in the
Configuration JSON editor left it stale in both directions: adding a UA
in JSON kept the switch off (and clicking it then replaced the custom
value with the default UA), removing it kept the switch on.

Add syncOpenclawUserAgentFromConfig to useOpenclawFormState and call it
from the OpenClaw JSON editor's onChange. It only reads valid JSON
objects, sets the switch to the case-insensitive presence of a
User-Agent header, never rewrites the JSON, and keeps the last state
while the draft is invalid.

Refs #8256

tests/hooks/useOpenclawFormState.test.tsx

@@ -171,3 +171,37 @@ it("reset tolerates null headers from JSON without rewriting settings", () => {
   expect(test.read()).toEqual(test.original);
   expect(test.onSettingsConfigChange).not.toHaveBeenCalled();
 });
+
+describe("useOpenclawFormState JSON editor sync", () => {
+  it("turns the switch on when a User-Agent is added in JSON", () => {
+    const test = mount(customHeaders);
+    expect(test.result.current.openclawUserAgent).toBe(false);
+    act(() =>
+      test.result.current.syncOpenclawUserAgentFromConfig(
+        JSON.stringify({
+          ...base,
+          headers: { ...customHeaders, "user-agent": "edited-agent" },
+        }),
+      ),
+    );
+    expect(test.result.current.openclawUserAgent).toBe(true);
+    expect(test.onSettingsConfigChange).not.toHaveBeenCalled();
+  });
+  it("turns the switch off when the User-Agent is removed in JSON", () => {
+    const test = mount({ ...customHeaders, "User-Agent": "fixture-agent" });
+    expect(test.result.current.openclawUserAgent).toBe(true);
+    act(() =>
+      test.result.current.syncOpenclawUserAgentFromConfig(
+        JSON.stringify({ ...base, headers: customHeaders }),
+      ),
+    );
+    expect(test.result.current.openclawUserAgent).toBe(false);
+  });
+  it("keeps the last state while the JSON draft is invalid", () => {
+    const test = mount({ "User-Agent": "fixture-agent" });
+    act(() =>
+      test.result.current.syncOpenclawUserAgentFromConfig('{"headers": {'),
+    );
+    expect(test.result.current.openclawUserAgent).toBe(true);
+  });
+});