fix(daemon): preserve hyphenated browser flags in arg serialization and lazy daemon startup (#2405)

When executing CLI subcommands with custom Chromium startup options
(such as `--use-fake-device-for-media-stream` or
`--use-file-for-fake-audio-capture=...`), two independent bugs
previously prevented flags from reaching `puppeteer.launch`:

1. Yargs Value Collision: `serializeArgs` emitted options and values as
detached token pairs (`['--chrome-arg', '--use-fake-device...']`). When
initializing the spawned daemon process, `yargs` interpreted the
hyphenated trailing token as an unrelated command option, stripping the
value from `--chrome-arg`.
2. Lazy Startup Parameter Dropping: When invoking action subcommands
against an inactive session, auto-start initialization called `start([],
sessionId)`. This hardcoded empty array silently discarded all browser
configuration flags passed on the invocation command line.

Fix:
- Enforce strict `--key=value` syntax in `serializeArgs`, compelling
`yargs` in the child daemon process to parse hyphenated payloads
strictly as string values.
- Forward `serializeArgs(cliOptions, argv)` during lazy subcommand
auto-start so implicit daemon instantiations inherit all requested
browser boot capabilities.

Includes comprehensive unit test coverage in
`tests/daemon/utils.test.ts` validating `--key=value` formatting across
scalar and array option serialization.

Fixes https://github.com/ChromeDevTools/chrome-devtools-mcp/issues/2406

---------

Co-authored-by: Alex Rudenko <alexrudenko@chromium.org>

src/bin/chrome-devtools.ts

@@ -263,7 +263,7 @@ for (const [commandName, commandDef] of Object.entries(commands)) {
       const sessionId = argv.sessionId as string;
       try {
         if (!isDaemonRunning(sessionId)) {
-          await start([], sessionId);
+          await start(serializeArgs(cliOptions, argv), sessionId);
         }
 
         const commandArgs: Record<string, unknown> = {};

src/daemon/utils.ts

@@ -128,10 +128,10 @@ export function serializeArgs(
       }
     } else if (Array.isArray(value)) {
       for (const item of value) {
-        args.push(`--${kebabKey}`, String(item));
+        args.push(`--${kebabKey}=${String(item)}`);
       }
     } else {
-      args.push(`--${kebabKey}`, String(value));
+      args.push(`--${kebabKey}=${String(value)}`);
     }
   }
   return args;

tests/daemon/utils.test.ts

@@ -26,7 +26,7 @@ describe('serializeArgs', () => {
       $0: 'test',
     } as unknown as ParsedArguments;
     const result = serializeArgs(options, argv);
-    assert.deepStrictEqual(result, ['--baz', 'value']);
+    assert.deepStrictEqual(result, ['--baz=value']);
   });
 
   it('should handle boolean values', () => {
@@ -41,15 +41,24 @@ describe('serializeArgs', () => {
     assert.deepStrictEqual(result, ['--foo', '--no-bar']);
   });
 
-  it('should handle array values', () => {
-    const options: Record<string, YargsOptions> = {foo: {}};
+  it('should handle array values including hyphenated flags', () => {
+    const options: Record<string, YargsOptions> = {foo: {}, chromeArg: {}};
     const argv = {
       foo: ['val1', 'val2'],
+      chromeArg: [
+        '--use-fake-device-for-media-stream',
+        '--use-file-for-fake-audio-capture=/tmp/test.wav',
+      ],
       _: [],
       $0: 'test',
     } as unknown as ParsedArguments;
     const result = serializeArgs(options, argv);
-    assert.deepStrictEqual(result, ['--foo', 'val1', '--foo', 'val2']);
+    assert.deepStrictEqual(result, [
+      '--foo=val1',
+      '--foo=val2',
+      '--chrome-arg=--use-fake-device-for-media-stream',
+      '--chrome-arg=--use-file-for-fake-audio-capture=/tmp/test.wav',
+    ]);
   });
 
   it('should handle primitive values', () => {
@@ -61,7 +70,7 @@ describe('serializeArgs', () => {
       $0: 'test',
     } as unknown as ParsedArguments;
     const result = serializeArgs(options, argv);
-    assert.deepStrictEqual(result, ['--foo', 'string', '--bar', '42']);
+    assert.deepStrictEqual(result, ['--foo=string', '--bar=42']);
   });
 
   it('should convert camelCase keys to kebab-case', () => {
@@ -77,8 +86,7 @@ describe('serializeArgs', () => {
     } as unknown as ParsedArguments;
     const result = serializeArgs(options, argv);
     assert.deepStrictEqual(result, [
-      '--camel-case-key',
-      'value1',
+      '--camel-case-key=value1',
       '--another-key',
     ]);
   });