feat(chat): --cwd 支持可选值，缺省为当前目录

使 --cwd 选项支持无值调用：
- --cwd 单独使用 → 默认为当前目录 "."
- --cwd /path → 使用指定路径
- --cwd=. / -C. → 等号或短选项语法

修复：--cwd 后接其他 flag 时被误认为值的歧义问题。

myclaude/commands/chat.py

@@ -12,21 +12,60 @@ from rich.console import Console
 from myclaude.project_root import get_myclaude_project_root
 
 console = Console()
+stderr_console = Console(stderr=True)
 
 
 def _resolve_chat_cwd() -> Path:
     root = get_myclaude_project_root()
     fallback = Path.home() / ".myclaude"
     if root == fallback:
-        console.print(
+        stderr_console.print(
             "[red]Cannot resolve myclaude project root.[/red] Run from the repo or set "
             "[cyan]MYCLAUDE_PROJECT_ROOT[/cyan].",
-            file=sys.stderr,
         )
         raise SystemExit(1)
     return root
 
 
+def _parse_cwd_from_args(args: list[str]) -> tuple[str | None, list[str]]:
+    """
+    Parse --cwd with optional value from args.
+
+    Returns (cwd_value, remaining_args).
+    --cwd alone -> cwd_value='.'
+    --cwd /path -> cwd_value='/path'
+    --cwd .     -> cwd_value='.'
+    """
+    cwd_value: str | None = None
+    remaining: list[str] = []
+    skip_next = False
+
+    for i, arg in enumerate(args):
+        if skip_next:
+            skip_next = False
+            continue
+
+        if arg in ("--cwd", "-C"):
+            # Check if next arg exists and is not a flag
+            if i + 1 < len(args) and not args[i + 1].startswith("-"):
+                cwd_value = args[i + 1]
+                skip_next = True
+            else:
+                # --cwd alone, default to current directory
+                cwd_value = "."
+        elif arg.startswith("--cwd="):
+            cwd_value = arg[6:]
+        elif arg.startswith("-C="):
+            cwd_value = arg[3:]
+        elif arg.startswith("-C") and len(arg) > 2:
+            # -C/path or -C.
+            cwd_value = arg[2:]
+        else:
+            remaining.append(arg)
+
+    return cwd_value, remaining
+
+
 @click.command(
     "chat",
     context_settings={
@@ -40,23 +79,47 @@ def _resolve_chat_cwd() -> Path:
     default=False,
     help="Forward to claude: bypass permission checks (sandbox / isolated use only).",
 )
+@click.option(
+    "--cwd",
+    "-C",
+    multiple=True,
+    metavar="PATH",
+    help="Working directory for claude (default: myclaude project root; '--cwd' uses current dir; '--cwd /path' uses specific path).",
+)
 @click.pass_context
-def chat_cmd(ctx: click.Context, dangerously_skip_permissions: bool) -> None:
-    """Run `claude` in the myclaude repo so CLAUDE.md and .claude/ apply; extra args pass through."""
+def chat_cmd(ctx: click.Context, dangerously_skip_permissions: bool, cwd: tuple[str, ...]) -> None:
+    """Run `claude` in the myclaude repo so CLAUDE.md and .claude/ apply; extra args pass through.
+
+    \b
+    Working directory options:
+      --cwd, -C           Use current directory as working directory
+      --cwd /path, -C/path  Use specified path as working directory
+      (none)              Use myclaude project root (default)
+    """
     binary = os.environ.get("CLAUDE_BIN") or shutil.which("claude")
     if not binary:
-        console.print(
+        stderr_console.print(
             "[red]claude CLI not found in PATH.[/red] Install Claude Code or set "
             "[cyan]CLAUDE_BIN[/cyan].",
-            file=sys.stderr,
         )
         raise SystemExit(127)
 
-    cwd = _resolve_chat_cwd()
+    # Parse --cwd from raw args since Click doesn't support optional values natively
+    # (We ignore the 'cwd' parameter from Click and parse manually from ctx.args)
+    cwd_value, remaining_args = _parse_cwd_from_args(ctx.args)
+
+    if cwd_value is None:
+        chat_cwd = _resolve_chat_cwd()
+    else:
+        chat_cwd = Path(cwd_value).resolve()
+        if not chat_cwd.is_dir():
+            stderr_console.print(f"[red]Not a directory:[/red] {cwd_value}")
+            raise SystemExit(1)
+
     cmd: list[str] = [binary]
     if dangerously_skip_permissions:
         cmd.append("--dangerously-skip-permissions")
-    cmd.extend(ctx.args)
+    cmd.extend(remaining_args)
 
-    proc = subprocess.run(cmd, cwd=str(cwd), check=False)
+    proc = subprocess.run(cmd, cwd=str(chat_cwd), check=False)
     raise SystemExit(proc.returncode)