feat(web): add interactive sidebar terminals

packages/api/terminal-controller/src/shells.ts

@@ -0,0 +1,28 @@
+/** Shell selection and executable verification use the target execution provider. */
+import type { SubprocessRuntime } from '@deepseek-ai/dsh-subprocess'
+import type { TerminalShell } from './types.ts'
+
+/**
+ * Resolve the configured shell or the execution environment's default shell.
+ * @param subprocess - target execution provider.
+ * @param configured - optional profile overriding the environment's default shell.
+ * @param signal - resolution cancellation.
+ * @returns one verified shell; a declared default that cannot resolve rejects.
+ */
+export async function resolveShell(
+  subprocess: SubprocessRuntime, configured: TerminalShell | undefined, signal: AbortSignal,
+): Promise<TerminalShell> {
+  let shell = configured
+  if (shell === undefined) {
+    const environment = await subprocess.terminalEnvironment(signal)
+    shell = profile(environment.defaultShell ?? (environment.platform === 'windows' ? 'cmd.exe' : '/bin/sh'))
+  }
+  const path = await subprocess.resolveExecutable(shell.path, undefined, signal)
+  return { ...shell, path }
+}
+
+function profile(path: string): TerminalShell {
+  const name = path.slice(Math.max(path.lastIndexOf('/'), path.lastIndexOf('\\')) + 1)
+  const kind = name.toLowerCase().replace(/\.exe$/u, '')
+  return { path, name, args: kind === 'cmd' ? [] : kind === 'pwsh' || kind === 'powershell' ? ['-NoLogo'] : ['-i'] }
+}