feat: Model based toolset switching (#111)

Co-authored-by: cpacker <packercharles@gmail.com>

src/tools/impl/Shell.ts

@@ -0,0 +1,72 @@
+import { bash } from "./Bash.js";
+import { validateRequiredParams } from "./validation.js";
+
+interface ShellArgs {
+  command: string[];
+  workdir?: string;
+  timeout_ms?: number;
+  with_escalated_permissions?: boolean;
+  justification?: string;
+}
+
+interface ShellResult {
+  output: string;
+  stdout: string[];
+  stderr: string[];
+}
+
+/**
+ * Codex-style shell tool.
+ * Runs an array of shell arguments, typically ["bash", "-lc", "..."].
+ */
+export async function shell(args: ShellArgs): Promise<ShellResult> {
+  validateRequiredParams(args, ["command"], "shell");
+
+  const { command, workdir, timeout_ms, justification: description } = args;
+  if (!Array.isArray(command) || command.length === 0) {
+    throw new Error("command must be a non-empty array of strings");
+  }
+
+  const commandString = command.join(" ");
+
+  const previousUserCwd = process.env.USER_CWD;
+  if (workdir) {
+    process.env.USER_CWD = workdir;
+  }
+
+  try {
+    const result = await bash({
+      command: commandString,
+      timeout: timeout_ms ?? 120000,
+      description,
+      run_in_background: false,
+    });
+
+    const text = (result.content ?? [])
+      .map((item) =>
+        "text" in item && typeof item.text === "string" ? item.text : "",
+      )
+      .filter(Boolean)
+      .join("\n");
+
+    const stdout = text ? text.split("\n") : [];
+    const stderr =
+      result.status === "error"
+        ? ["Command reported an error. See output for details."]
+        : [];
+
+    return {
+      output: text,
+      stdout,
+      stderr,
+    };
+  } finally {
+    if (workdir) {
+      if (previousUserCwd === undefined) {
+        delete process.env.USER_CWD;
+      } else {
+        process.env.USER_CWD = previousUserCwd;
+      }
+    }
+  }
+}