fix(workspace): keep the default Workspace path language-neutral

The first-use directory name and its stored title came from the Client's
startup language, so one product decision carried two incompatible
requirements: a path addressed by shell commands, tool arguments, @path
references, and session logs, and a label a reader reads.

The controller now owns the fixed `default-workspace` directory name and
the registry titles the Workspace after that same segment, so
`workspace.initializeDefault` takes no request at all —
WorkspaceInitializeDefaultRequest and its name validation are gone, and
the registry resolver returns a path instead of a path and title. No
language reaches the Host.

Browser consumers label a Workspace through the new
`workspaceDisplayTitle`: a title still equal to the automatic one reads
as the localized default name from the `common` namespace, every other
title reads verbatim. The Workspace browser resolves it once at the store
read, so rows, hover card, search meta, and the rename and delete dialogs
inherit it; the hero picker and the Conversation chip resolve it too.
Confirming a rename stores the text on screen, which is what stops a row
following the language.

packages/api/workspace-controller/src/default-directory.ts

@@ -3,6 +3,7 @@
 import { homedir } from 'node:os'
 import { posix, win32 } from 'node:path'
 import { runNativeCommand, type NativeCommandRunner } from '@deepseek-ai/dsh-native-command'
+import { DEFAULT_WORKSPACE_DIRECTORY } from './default-workspace.ts'
 
 /** Platform observations replaceable in directory-resolution tests. */
 interface DocumentsDirectoryInternals {
@@ -28,14 +29,12 @@ export function validateDocumentsDirectory(directory: string, platform: NodeJS.P
 
 /**
  * Resolve the first-use directory on the Host without creating files.
- * @param directoryName - validated single directory name supplied by the Client.
  * @param documentsDirectory - explicit deployment override for the system Documents directory.
  * @param signal - caller lifetime and lookup deadline.
  * @param internals - platform facts and native command runner.
  * @returns the absolute candidate path.
  */
 export async function defaultWorkspaceDirectory(
-  directoryName: string,
   documentsDirectory: string | undefined,
   signal: AbortSignal,
   internals: DocumentsDirectoryInternals = {},
@@ -75,5 +74,5 @@ export async function defaultWorkspaceDirectory(
   }
   directory = validateDocumentsDirectory(directory, platform)
   signal.throwIfAborted()
-  return paths.join(directory, 'deepseek-harness', directoryName)
+  return paths.join(directory, 'deepseek-harness', DEFAULT_WORKSPACE_DIRECTORY)
 }