feat(11-01): create stealth fingerprint masking module

- Add StealthConfig Pydantic model with all playwright-stealth options
- Add apply_stealth_sync/apply_stealth_async functions for browser context
- Add get_default_stealth_config convenience function
- Add 9 unit tests covering config defaults, stealth application, and disabled mode
- Update conftest.py with stealth_config and mock_browser_context fixtures

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

kb_workflow/crawler/stealth/__init__.py

@@ -0,0 +1,15 @@
+"""Stealth module for browser fingerprint masking."""
+
+from .stealth_config import (
+    StealthConfig,
+    apply_stealth_sync,
+    apply_stealth_async,
+    get_default_stealth_config,
+)
+
+__all__ = [
+    "StealthConfig",
+    "apply_stealth_sync",
+    "apply_stealth_async",
+    "get_default_stealth_config",
+]

kb_workflow/crawler/stealth/stealth_config.py

@@ -0,0 +1,169 @@
+"""Stealth configuration for browser fingerprint masking.
+
+Uses playwright-stealth library to hide Playwright automation signatures.
+"""
+
+from typing import Optional
+from playwright.sync_api import BrowserContext
+from playwright.async_api import BrowserContext as AsyncBrowserContext
+from pydantic import BaseModel, Field
+from playwright_stealth import Stealth
+
+
+class StealthConfig(BaseModel):
+    """Configuration for browser stealth settings.
+
+    All options map to playwright-stealth evasion scripts.
+    Default values optimized for Zhihu anti-detection.
+    """
+
+    stealth_enabled: bool = Field(
+        default=True,
+        description="Enable stealth mode (set False to disable)"
+    )
+
+    # Navigator evasion options
+    navigator_webdriver: bool = Field(
+        default=True,
+        description="Hide navigator.webdriver property (STEALTH-01)"
+    )
+    navigator_user_agent: bool = Field(
+        default=True,
+        description="Replace HeadlessChrome in User-Agent (STEALTH-04)"
+    )
+    navigator_plugins: bool = Field(
+        default=True,
+        description="Mock navigator.plugins array"
+    )
+    navigator_languages: bool = Field(
+        default=True,
+        description="Set navigator.languages"
+    )
+    navigator_platform: bool = Field(
+        default=True,
+        description="Set navigator.platform"
+    )
+    navigator_vendor: bool = Field(
+        default=True,
+        description="Set navigator.vendor"
+    )
+    navigator_permissions: bool = Field(
+        default=True,
+        description="Override navigator.permissions"
+    )
+
+    # Chrome object evasion (STEALTH-03)
+    chrome_app: bool = Field(
+        default=True,
+        description="Mock chrome.app object"
+    )
+    chrome_csi: bool = Field(
+        default=True,
+        description="Mock chrome.csi function"
+    )
+    chrome_load_times: bool = Field(
+        default=True,
+        description="Mock chrome.loadTimes function"
+    )
+
+    # WebGL and rendering
+    webgl_vendor: bool = Field(
+        default=True,
+        description="Override WebGL vendor/renderer strings"
+    )
+
+    # Other evasion options
+    hairline: bool = Field(
+        default=True,
+        description="Fix hairline detection"
+    )
+    iframe_content_window: bool = Field(
+        default=True,
+        description="Fix iframe contentWindow"
+    )
+    media_codecs: bool = Field(
+        default=True,
+        description="Mock media codecs"
+    )
+    error_prototype: bool = Field(
+        default=True,
+        description="Fix error prototype chain"
+    )
+    sec_ch_ua: bool = Field(
+        default=True,
+        description="Set sec-ch-ua headers"
+    )
+
+    def create_stealth(self) -> Stealth:
+        """Create playwright-stealth Stealth instance from config.
+
+        Returns:
+            Configured Stealth instance
+        """
+        return Stealth(
+            navigator_webdriver=self.navigator_webdriver,
+            navigator_user_agent=self.navigator_user_agent,
+            navigator_plugins=self.navigator_plugins,
+            navigator_languages=self.navigator_languages,
+            navigator_platform=self.navigator_platform,
+            navigator_vendor=self.navigator_vendor,
+            navigator_permissions=self.navigator_permissions,
+            chrome_app=self.chrome_app,
+            chrome_csi=self.chrome_csi,
+            chrome_load_times=self.chrome_load_times,
+            webgl_vendor=self.webgl_vendor,
+            hairline=self.hairline,
+            iframe_content_window=self.iframe_content_window,
+            media_codecs=self.media_codecs,
+            error_prototype=self.error_prototype,
+            sec_ch_ua=self.sec_ch_ua,
+        )
+
+
+def apply_stealth_sync(
+    context: BrowserContext,
+    config: Optional[StealthConfig] = None
+) -> None:
+    """Apply stealth settings to browser context (synchronous).
+
+    Args:
+        context: Playwright BrowserContext to apply stealth to
+        config: StealthConfig instance (uses defaults if not provided)
+    """
+    if config is None:
+        config = StealthConfig()
+
+    if not config.stealth_enabled:
+        return
+
+    stealth = config.create_stealth()
+    stealth.apply_stealth_sync(context)
+
+
+async def apply_stealth_async(
+    context: AsyncBrowserContext,
+    config: Optional[StealthConfig] = None
+) -> None:
+    """Apply stealth settings to browser context (asynchronous).
+
+    Args:
+        context: Playwright async BrowserContext to apply stealth to
+        config: StealthConfig instance (uses defaults if not provided)
+    """
+    if config is None:
+        config = StealthConfig()
+
+    if not config.stealth_enabled:
+        return
+
+    stealth = config.create_stealth()
+    await stealth.apply_stealth_async(context)
+
+
+def get_default_stealth_config() -> StealthConfig:
+    """Get default StealthConfig for Zhihu crawling.
+
+    Returns:
+        StealthConfig with all evasion options enabled
+    """
+    return StealthConfig()