feat(mcp): register ast-grep as built-in MCP

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/oh-my-openagent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

src/mcp/ast-grep.ts

@@ -0,0 +1,97 @@
+import { existsSync } from "node:fs";
+import { dirname, resolve } from "node:path";
+import { fileURLToPath } from "node:url";
+import type { LocalMcpConfig } from "./lsp";
+
+const PACKAGE_REL = "packages/ast-grep-mcp";
+const DIST_CLI_REL = "dist/cli.js";
+const SOURCE_CLI_REL = "src/cli.ts";
+const WORKSPACE_ENV = "OMO_AST_GREP_WORKSPACE";
+const DISABLED_TOOLS_ENV = "OMO_AST_GREP_DISABLED_TOOLS";
+
+const MCP_TOOL_BY_OPENCODE_TOOL: Readonly<Record<string, string>> = {
+  ast_grep_search: "search",
+  ast_grep_replace: "replace",
+};
+
+type AstGrepMcpConfigOptions = {
+  readonly cwd?: string;
+  readonly disabledTools?: readonly string[];
+  readonly moduleUrl?: string;
+  readonly exists?: (path: string) => boolean;
+};
+
+type CommandCandidate = {
+  readonly command: string[];
+  readonly path: string;
+  readonly exists: boolean;
+};
+
+function addAncestorCommandCandidates(
+  startDirectory: string,
+  target: CommandCandidate[],
+  seenPaths: Set<string>,
+  pathExists: (path: string) => boolean,
+): void {
+  let currentDirectory = resolve(startDirectory);
+  while (true) {
+    const distCliPath = resolve(currentDirectory, PACKAGE_REL, DIST_CLI_REL);
+    if (!seenPaths.has(distCliPath)) {
+      seenPaths.add(distCliPath);
+      target.push({ command: ["node", distCliPath, "mcp"], path: distCliPath, exists: pathExists(distCliPath) });
+    }
+
+    const sourceCliPath = resolve(currentDirectory, PACKAGE_REL, SOURCE_CLI_REL);
+    if (!seenPaths.has(sourceCliPath)) {
+      seenPaths.add(sourceCliPath);
+      target.push({ command: ["bun", sourceCliPath, "mcp"], path: sourceCliPath, exists: pathExists(sourceCliPath) });
+    }
+
+    const parentDirectory = resolve(currentDirectory, "..");
+    if (parentDirectory === currentDirectory) return;
+    currentDirectory = parentDirectory;
+  }
+}
+
+function getModuleDirectory(moduleUrl: string): string | null {
+  try {
+    return dirname(fileURLToPath(moduleUrl));
+  } catch {
+    return null;
+  }
+}
+
+function resolveAstGrepCommand(options: AstGrepMcpConfigOptions = {}): string[] {
+  const pathExists = options.exists ?? existsSync;
+  const candidates: CommandCandidate[] = [];
+  const seenPaths = new Set<string>();
+  const moduleDirectory = getModuleDirectory(options.moduleUrl ?? import.meta.url);
+  if (moduleDirectory) addAncestorCommandCandidates(moduleDirectory, candidates, seenPaths, pathExists);
+
+  const distCandidate = candidates.find((candidate) => candidate.path.endsWith(DIST_CLI_REL) && candidate.exists);
+  if (distCandidate) return distCandidate.command;
+  const sourceCandidate = candidates.find((candidate) => candidate.path.endsWith(SOURCE_CLI_REL) && candidate.exists);
+  if (sourceCandidate) return sourceCandidate.command;
+  return candidates[0]?.command ?? ["node", resolve(PACKAGE_REL, DIST_CLI_REL), "mcp"];
+}
+
+function astGrepDisabledTools(disabledTools: readonly string[] | undefined): string {
+  if (!disabledTools) return "";
+  return disabledTools
+    .map((toolName) => MCP_TOOL_BY_OPENCODE_TOOL[toolName])
+    .filter((toolName): toolName is string => typeof toolName === "string")
+    .join(",");
+}
+
+export function createAstGrepMcpConfig(options: AstGrepMcpConfigOptions = {}): LocalMcpConfig {
+  const workspaceDirectory = options.cwd ?? process.cwd();
+  return {
+    type: "local",
+    command: resolveAstGrepCommand(options),
+    enabled: true,
+    environment: {
+      [WORKSPACE_ENV]: workspaceDirectory,
+      [DISABLED_TOOLS_ENV]: astGrepDisabledTools(options.disabledTools),
+    },
+  };
+}