feat(app): add workspace toggle command to command palette and prompt input

[alexyaroshuk]

closes #11813

Summary

This PR adds a new command to toggle workspaces, accessible via the command palette and the prompt input slash command menu.

What does this PR do?

1. Adds workspace toggle command to command palette (packages/app/src/pages/layout.tsx):
   • New command ID: workspace.toggle
   • Category: Workspace
   • Accessible via Ctrl/Cmd+Shift+P → search "Toggle workspaces"

2. Adds slash command support (packages/app/src/pages/layout.tsx):
   • Slash trigger: /workspace
   • Appears in the prompt input's slash command menu

3. Adds toast notifications (packages/app/src/pages/layout.tsx):
   • Shows confirmation when workspaces are enabled/disabled via command to make it obvious the command was applied
   • Toast messages in all 15 supported languages

4. Adds translations (packages/app/src/i18n/*.ts):
   • Command title and description (English only for description)
   • Toast messages for enabled/disabled states

How did you verify your code works?

• e2e test: same pass/fail
• manual testing:

A. From prompt input:

1. type '/workspace'
2. new command shows up, description is correct
3. click the command
4. observe that workspace mode is toggled
5. toast is correct

B: From command pallete:

1. type 'workspace'
2. See 'toggle workspace' command, description is correct
3. call the command
4. observe that workspace mode is toggled
5. toast is correct

[github-actions]

Hey! Your PR title Add workspace toggle command to command palette and prompt input doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

[github-actions]

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No duplicate PRs found