fix(cli): serialize object daemon arguments (#2797)

## Summary

Fix daemon argument serialization for object-valued CLI options.

`serializeArgs()` currently falls back to `String(value)` for
non-boolean, non-array values. Yargs parses options such as `wsHeaders`
into an object, so direct serialization produces `[object Object]` and
the daemon cannot reconstruct the value.

This change serializes object values with `JSON.stringify()` while
preserving the existing behavior for primitive, boolean, and array
options.

## Review follow-up

The earlier review also identified CLI-injected `isolated` / `headless`
defaults interacting badly with `--config`. Current upstream `main` has
since removed those assignments entirely, so after rebasing there is no
additional default-guard change to carry in this PR.

## Validation

- focused `serializeArgs` regression for object values
- `git diff --check`

Signed-off-by: Robert McConnell <robert@mcc0nnell.org>

src/daemon/utils.ts

@@ -189,7 +189,9 @@ export function serializeArgs(
         args.push(`--${kebabKey}=${String(item)}`);
       }
     } else {
-      args.push(`--${kebabKey}=${String(value)}`);
+      const serializedValue =
+        typeof value === 'object' ? JSON.stringify(value) : String(value);
+      args.push(`--${kebabKey}=${serializedValue}`);
     }
   }
   return args;

tests/daemon/utils.test.ts

@@ -125,6 +125,21 @@ describe('serializeArgs', () => {
     assert.deepStrictEqual(result, ['--foo=string', '--bar=42']);
   });
 
+  it('should serialize object values as JSON', () => {
+    const options: Record<string, YargsOptions> = {wsHeaders: {}};
+    const argv = {
+      wsHeaders: {
+        Authorization: 'Bearer token',
+      },
+      _: [],
+      $0: 'test',
+    } as unknown as ParsedArguments;
+    const result = serializeArgs(options, argv);
+    assert.deepStrictEqual(result, [
+      '--ws-headers={"Authorization":"Bearer token"}',
+    ]);
+  });
+
   it('should convert camelCase keys to kebab-case', () => {
     const options: Record<string, YargsOptions> = {
       camelCaseKey: {},