refactor(utils): modularize websearch-manager into websearch/ directory

- extract gemini-cli, grok-cli, opencode-cli providers

- extract hook-config, hook-env, hook-installer, status, types

- slim websearch-manager.ts from 867 to 103 lines (88% reduction)

- add barrel export at websearch/index.ts

src/utils/websearch/opencode-cli.ts

@@ -0,0 +1,85 @@
+/**
+ * OpenCode CLI Detection
+ *
+ * Detects and manages OpenCode CLI installation status.
+ *
+ * @module utils/websearch/opencode-cli
+ */
+
+import { execSync } from 'child_process';
+import type { OpenCodeCliStatus } from './types';
+
+// Cache for OpenCode CLI status (per process)
+let opencodeCliCache: OpenCodeCliStatus | null = null;
+
+/**
+ * Check if OpenCode CLI is installed globally
+ *
+ * OpenCode provides built-in web search via opencode/grok-code model.
+ * Install: curl -fsSL https://opencode.ai/install | bash
+ *
+ * @returns OpenCode CLI status with path and version
+ */
+export function getOpenCodeCliStatus(): OpenCodeCliStatus {
+  // Return cached result if available
+  if (opencodeCliCache) {
+    return opencodeCliCache;
+  }
+
+  const result: OpenCodeCliStatus = {
+    installed: false,
+    path: null,
+    version: null,
+  };
+
+  try {
+    const isWindows = process.platform === 'win32';
+    const whichCmd = isWindows ? 'where opencode' : 'which opencode';
+
+    const pathResult = execSync(whichCmd, {
+      encoding: 'utf8',
+      timeout: 5000,
+      stdio: ['pipe', 'pipe', 'pipe'],
+    });
+
+    const opencodePath = pathResult.trim().split('\n')[0]; // First result on Windows
+
+    if (opencodePath) {
+      result.installed = true;
+      result.path = opencodePath;
+
+      // Try to get version
+      try {
+        const versionResult = execSync('opencode --version', {
+          encoding: 'utf8',
+          timeout: 5000,
+          stdio: ['pipe', 'pipe', 'pipe'],
+        });
+        result.version = versionResult.trim();
+      } catch {
+        // Version check failed, but CLI is installed
+        result.version = 'unknown';
+      }
+    }
+  } catch {
+    // Command not found - OpenCode CLI not installed
+  }
+
+  // Cache result
+  opencodeCliCache = result;
+  return result;
+}
+
+/**
+ * Check if OpenCode CLI is available (quick boolean check)
+ */
+export function hasOpenCodeCli(): boolean {
+  return getOpenCodeCliStatus().installed;
+}
+
+/**
+ * Clear OpenCode CLI cache (for testing or after installation)
+ */
+export function clearOpenCodeCliCache(): void {
+  opencodeCliCache = null;
+}